We know that some of the other Star Wars languages were fairly well developed by the movie's creators, in terms of vocabulary, grammar, etc. Was the Wookiee language designed in this level of detail or did they just try to put together sounds that made sense emotionally?
Shyriiwook was definitely not fully designed (especially for the movies) in a Tolkienesque tradition out-of-Universe.
It was just a set of phrases, listed on the Wikia. Most of them were invented for later EU C-canon.
Shyriiwook is a sound effect from the first movie, so there would be continuity issues if it were to be converted into a language, especially if backwards compatibility was taken into account, in the sense of making the new language either sound like the original sound effects or in the sense of making the old sound effects mean something.
1) The language would almost certainly be practically impossible for actors to speak. Machine generated grammatical Shyriiwook might be possible, but the director would have a harder time hitting the emotional qualities. (The general rise and fall of tones of Shyrriwook needs to match up to English/Human so that the audience can tell if Chewie is happy or sad)
2) A human spoken language wouldn't sound like the sound effects.
3) The logotome (the set of possible words) appears to have too many words in the same space, i.e. the words sound too similar. I don't know if this would just make it difficult or impossible to learn. For example, in a hypothetical Shyriiwook word, you might trill the "r" for a beat and that means one thing, trill it for two beats, it means something else, trill and r for three beats and it means a third thing. Could people distinguish them?