The faults I personally find in Esperanto:1. It's mostly regular, but not completely. I'd make it completely regular at all times - all words that seem to be compound words would be replaced with words that don't. For example, "papero - paper" looks like it has the suffix "ero - a fragment" attached to the word "pap - pope". There's also some things that are regular but some people don't know (and assume that they aren't) just because the original rules were a bit unclear about it - I'd basically clarify the rules. For example, someone made a Wikipedia page where they most likely just directly translated the word "lavender" from English (as it's closer to "lavand" in most other languages and in the original Latin name), to be "lavendo". In fact, in Esperanto, "lav" means "wash" and "endo" means "a required thing", so lavendo already means "a thing that needs to be washed". "Lavando" meanwhile, would be completely safe to use. If words were always regular, then this wouldn't happen so easily because people would always keep it in mind. 2. There's some irregularity in the personal pronouns - for example, "mia" means "my", but "kia" means "what kind of, what sort of" instead of "what's, whose". It's actually "kies" that means "whose". However "kie" means "where", and "kiea" means "where's" (as in the possessive, not "where is"). Similarly, normally the prefix "mal - opposite" is used, or "ne - no, not", when talking about certain things that are "nots" and "opposites". But when saying terms like "nothing, nobody" (no things; no bodies; the opposite of "everybody, every thing"), there's a mysterious extra letter that has been attached to the words. Iam means "sometime, at some unknown time", and ĉiam means "always, at all times", but when saying "never, at no time" instead of "neiam, malĉiam" which would be more expected, the official word is mysteriously "neniam". (Although some people do use "malĉiam", I'm not sure about "neiam" or "ne iam".) 3. In English, we have the words "who/which/that" which refers back to the thing that was previously stated, and change depending on if the thing is a living creature or not. So we say "The man who" but "the chair that/which". In Swedish and Indonesian, they have this same word ("som" in Swedish, and generally "yang" in Indonesian), but it doesn't ever change form and they use the same word for living and non-living things. ("The man who, the chair who".) Japanese doesn't have any such word like this at all, instead needing to use some descriptive phrase like "the received letter; the came man" (the letter which was received, the man who came).
In Esperanto, this word changes between if it's plural (kiuj) or singular (kiu), or in the accusative (kiun, kiujn) or not. It doesn't change according to if the thing being referred to is living or non-living. I would use another word that doesn't change form. Kiu is often confusing on if/when it takes the accusative case or not, and many languages don't have it to begin with. Even those who have it in our language tend to find it difficult. For example:
la homo kiu parolis
= the person who talked
mi batis la homon kiu(n) parolis
= I hit the person who(m) talked.
Does the accusative case (the "n") go here in order to match the one on "homo - a human" since we're referring to the same thing, or not? Most people don't know.
la ŝtonoj kiuj rompiĝis
= the stones which/that became broken
mi rompigis la ŝtonojn kiuj(n) malfortis
= I broke the stones which/that were weak
Perhaps there's some sense in having this word act like it does, and perhaps in another year of knowing Esperanto I'll see it, but for now I don't.If I were to go further and actually re-create Esperanto: 1. I would remove the ĥ-sound as it's hardly used to begin with, as many people don't have it in their languages and as many people find that it sounds ugly. The look and sound of Esperanto is really unfortunate in most people's opinions, and if I could I'd fix that - but once you're actually good at language, you cease to notice it and it becomes simply "language". Anyway, a "simple, international" language doesn't need extra sounds. The reason why Esperanto looks like it does is reportedly because "Asians, Africans, and everyone else will learn a European-looking language - but the majority of Europeans would never learn, say, an Asian language." As his only hope was to draw in Europeans first and then get the language spread to other countries, he felt that making it look like a jumbled mess of Romance, Germanic and Slavic would help it take the best hold, because it would seem more familiar. Plus at that time, whether France liked it or not would likely make or break the language's chances ; D 2. I would remove the letter c, as it is simply the "ts" sound, and make it clearly spelled with "ts". That way, pronunciation abominations such as "scienco - science", which is actually pronounced "stsientso", would be avoided as more people would think about how the word actually sounds, not how it looks or sounds in languages like English. The reason why it exists in the first place is to keep the vocabulary looking more immediately-recognizable, so that more people will want to learn it. "Saienso" is less obvious to the eye than "scienco". However, in light of all the languages like Japanese and Icelandic that change the spelling of a foreign word in order to make it match their own language's pronunciation, this doesn't make much sense to me. 3. I'd make all root words rather short - for example, some longer longer words like "proksima (nearby, close)", "konvinko (conviction)", "pantalono (trousers)", and "civilizo (civilization)" would be shortened to something like "proka, konvo, panto, civo", or replaced with other words (such as "troso; trousers") that would look less irregular or would seem easier to pronounce. A language that can compound heavily needs to have short words. Although this is gradually happening on its own - words are being shortened (civilizo used to be civilizacio), or synonyms that are shorter are filtering in ("malproksima" has the synonym "fora") - I'd have kept this in mind from the beginning. There's actually not all that many words that are that long, it's just really annoying to write something like "pantalonvestante". If I were to fix Esperanto's culture: (By the way, this is stuff I actually plan to do years in the future whenever I have enough money to afford stuff like paid website hosting and hiring coders... Yeah I wish.) 1. There would be a big online forum, where you could talk about anything at all... that wasn't "lernu.com". It wouldn't be for learners, and it wouldn't be about Esperanto. It'd be about real life and your newborn baby and hacking Pokemon and whatever else you'd normally talk about on a forum. The only reason for why none seems to exist is probably because lernu works "well enough", and all the people with money enough to host a nice forum aren't so into being on the internet. The site navigation would be entirely in Esperanto and people would be able to donate money to keep the forum ad-free, but any extra money would go towards something like stipends and grants. If you had a project idea that had to do with Esperanto (ex. creating a dictionary, videogame, cartoon, documentary, periodical...) you could get some monetary support through the leftover donation money. Priority would go towards people who were making things for disabled people (ex. Braille periodicals) and for language-teaching books (ex. a textbook in Esperanto for learning Japanese). 2. There would be a fiction archive site where you could post fiction in Esperanto of all kinds. It would be entirely in Esperanto (though perhaps you'd be able to upload tranlations to other languages). So you could post fanfic, or poetry, or your own original short stories. It's not just about having an archive, but many people who've just started to learn Esperanto would love such a site for reading practise and none exists. A donation option would exist and then it would be exactly like with the forum. 3. There would be a language council that you can actually easily submit words to, and they would be able to help you think of how to say what you want in Esperanto, so you wouldn't have to use a new word. If they couldn't, then they would say it was okay to borrow the word, and would add it to a list of words on their site. They would have a published list of all the "accepted" words, along with a published list of officially non-accepted words with their accepted alternatives. So in another column would be the words in a few other languages that people had sent in when asking about it, so people could simply search "blog" in English and find the correct term for example. (Or there would be another, similar system that would be easier to handle.) Now, people might completely ignore these lists (as they do with Swedish lists of a similar nature), but it would still seem a lot more organized and it would help keep people from saying "blogo, animeo (blog, anime)". Ex. "freŝigo", "an until-date-cause", is what many people use for "update" despite that it's not at all immediately apparent what the word means - it sounds like it means more like to stamp something with an expiration date. In fact they should use something more like "freŝigo, novigo" - fresh-cause, new-cause, as it makes a lot more sense. They could even use a simpler word, like "became edited". The point in Esperanto is to be able to read something and understand it, not to literally translate a word from English that doesn't even make any sense to begin with ("up + date"?). Likewise, this language site would have grammar information that was not obtained "through popular usage", but that was only Zamenhof's real grammar rules, and that was summarized and clearly explained. Examples of popular usage could also exist, but be outside of that. Too many people teach the "trends" as if they were the "rules". Likewise, the big, popular dictionaries are full of WAY too many new, unnecessary words - they don't stop to think about how the word could be said with a compound word. They don't even stop to think about how when you're writing a dictionary definition for something like "cat", you probably shouldn't use rare words in the definition. So that same kind of language committee should probably have their own dictionary that marks which words are in common use and which aren't (because a beginner certainly doesn't know).