I noticed that your question was in
1) While traveling to locations in Adventure mode often these seem underwhelming because they are very similar to each other or simple in terms of design or the design is completely absent (like elves or underworld civs villages). Have you ever considered, including the community in order to help build these designs using a contest? The winners could be awarded a mention in the description to a statue in the specific construction.
We now have a Lua implementation, so new building generation could become data-driven in a system that's more powerful than raws. The last time I recall Tarn implementing community submissions was for material densities and color strings, the latter of which was fairly immaterial (at the time) outside a dwarf randomly liking the color of a certain thing. There's no in-world credit, either, they're mainly attributed in the files.
3) Have you considered simplifying the clothing size system so that humanoids can wear clothes with less restrictions? For Example clothing could be divided into 3 size categories ( Small, Medium, Large and maybe XL ) to accomodate all creatures
The sizing system is currently based on adult body volume, which can vary to a huge degree among creatures. It's somewhat of a simplification from some of the earliest versions where dwarves had a [STOUT] tag that served as an additional fitting category.
I agree that clothesmaking should just be fire-and-forget and as long as you have workshops running you should be able to meet demand. I don't think that simplifying the size brackets is a permanent solution. There would still be situations where clothing for certain creatures is unusable in some way. You could collapse humans and dwarves into the same bracket, proclaim the immigration restrictions are safe to open, and then you'll still have a situation where you can't adequately dress your ogres and kobolds.
I was chatting with Putnam a while back, there's a lot of ways that the fitting system could have even more restrictions, sized for a specific unit's appearance modifiers and limb counts. Baby centaur trousers, never worn. This sort of specificity would be more relevant for making armor, where you're already incentivized to make specialty goods for a limited number of units.
4) I know that a cave rework is currently planned for a future update but, I think it would be very nice to have the option to stop cave grass & vegetation from mixing together turning every cave in the same mixed biome after a few years in game.
I second this, particularly with the different relation to negative space that premium graphics have. Grass now has to have edging, which makes what was bunch of commas in different colors look messier than intended. Before v50, there were only two species of cave grass that mixed on the same layer anyways.
I'd also want
larger clumps of a single grass type for surface grass, as well. It's mainly noticeable in good biomes, but there's a few mods that add unique grass sprites and have to work around the structure the game gives for grass.