to my best knowledge;
- you already can replace all the vanilla textures that exist with hires textures, so we already are at 100%, and there is no more percent beyond 100 in this case
- the engine already supports objects with a lot of polys, and even oldDark did if memory serves, so this never was a problem, all you need to do is to actually create the objects
- no idea what you mean with the highs and lows
- pretty sure you can have really long audio if you want, but doing so is considered bad practice
- NewDark pushed this pretty high already if memory serves, again, if you are running out of objects than there is a pretty good chance you are doing it wrong
- I think someone here mentioned that the current (brush?) limit is suspiciously close to max a 32bit engine can do, so we are most likely already maxed here
- hard to tell whether new brush shapes are possible, and even if, is there really a demand for them?
- afaik, texture transparencies work properly as long as you don't mess your textures up, so if they are broken ingame, you did something wrong
- personal advice: if you don't want bad performance in places with bad performance, don't create places with bad performance by doing things that lead to bad performance
I might be wrong of course, but pretty sure someone will correct me if that's the case.