As for late-game resource hogging, it definetely seems like an area that needs improvement. Compiling to x64 would relieve the memory-storage issues (at least if you have lots of ram and a x64 system), but I know that is another discussion.
And an integrated programming language for modding would be absolutely brilliant, as the RAW's are rather awkward (but this would be a very large undertaking).
I dont honostly think the interface is
that bad, but a few tweaks would massively help (eg remembering scroll positon, more helpful error messages (instead of "b"-"d"
No Door, which is extreemly unhelpful to a new player), better categorisation etc)
Improvements to the AI and whatever else so forts are not made invincible by walling/walling-cage-traps etc (I know this is a goal, but at the moment its quite an issue).
Improvements to the graphics. Yes that always lets off a sigh, but personally I wouldn't want much. Just a unique tile per thing (so my gears dont look like gems or vice versa). I generally play in ASCII because I dont like my gears looking like gems and similar issues.
And bugs. Always an issue. Some seriously annoying ones have been around forever. Toady as started work fixing some though (no more walling-self-in!
), and this is excellent.
Also combat. The damage model has issues with some things (eg bruising is basically nothing, rotting cant fully rot something, burning cant fully burn something etc), and combat seems to spontaneous. As in someone will either chip your nail or chop your head off.