Love the game, have played well over 200 hours probably, and I certainly have a proficiency with most things in Dwarf Fortress. Played Nethack and MUDs some a long time ago, love randomization+rpg and so on.
This game truly is a work of art before the official recognition. The obvious issues are graphics, user interface, and to a lesser extent some features left quasi-functional or vestigial bugs.
I think solving graphics is probably going to be a long hard haul, though some work has been made on that front, but user interface and general playability can be addressed directly by Toady.
The thing is, he prefers to add features (which is great), but doesn't like to change user interface and such because he is going to hate going back and changing it later. But, people are going to play the game for 10-20 more years before it is released, with the current bad interface and related issues.
So, the solution is: start a kickstarter, raise a ton of money, and essentially hire Toady as a code mercenary for a just 1 year to make things better for the next 20.
This could work because:
1. He's on track to release a new big version soon, so he has just implemented a ton of features and could feasibly switch gears to something else for a bit. The timing seems right, particularly because he is likely going to be over version .40, i.e. 40% completion to full 1.0 release.
2. He lives off donations already, and on a good year makes about 50,000$. He already has a large playerbase that is accustomed to paying him. Any decent drive could hit 100,000$ pretty much without fail, and 150,000 seems even more likely to be honest.
3. This is something a lot of Dwarf Fortress players would want, because it is essentially an investment of money to save them massive amounts of time. Toady making the game not take forever to do simple things will add up to a lot of time saved over the next 1 or 2 decades.
4. It could mandate only a year need be spent on it, which in the long course of things would not interfere with his 20-30 year strategy much at all.
5. It does not need to include any other developer, only hiring Toady to do the job, which is a concern he has made clear in interviews. He likes to be familiar with his own code.
6. It is something he's going to have to do eventually, so the only obstacle is, like he has mentioned himself, that as other features are added, UI functionality will be added and some things will have to be uprooted and redone later. This is still him working on his game towards a 1.0 release.
7. The kickstarter would demonstrate a kind of popular vote from the playerbase. If this is something that DF players really want, and would pay a lot to get, then that could influence the good-natured Tarn we all know and love. Could really strike a chord with the guy.
8. Plethora of easily implementable playability suggestions are listed on the forums. Lots of low hanging fruit. Even a 6 month patch could work wonders.
9. The only extra backer reward necessary would be the patch. He could set a threshold value for the regular crayon art & stories if he thinks he couldn't possibly dedicate that much time and crayon to a large number of donators.
In the end this one year spent fine tuning the game would really pay off big. It could provide Toady with easy money, and the one string attached would be 1 year of working on his own game how he sees fit, limited only to this one less appealing aspect of it. It would make playing the game demonstrably better for decades, and it could quite easily be done.
The only problems:
1. Toady just might not want to. He has dedicated his life to this game, and always done only what he wants, so his whims are the ultimate trump card in the matter. It is his decision what to do with his game and when.
2. He has received large monetary offers in the past (300,000$) and rejected them. It was to buy the rights I believe, but it still shows he is resistant to financial pressure. That's why he quit his job to work on it full time, obviously.
3. Tarn might actually take offense. See it as "telling him what to do with his creation" kind of thing. Some people get that way about their art.
4. Toady would have to setup the kickstarter. We don't want anyone "raising the money" for him. Might end in kobold thievery. Even an overhead would be uncalled for, since he has his own donation setup. Just no reason to let anyone else do it, but that means he must make the kickstarter page himself.
5. The kickstarter could fail. His normal donations are steady, so I see this as pretty remote. Also consider how cheap knockoffs get tons more money (Rimworld - 250,000, Stonehearth - 750,000). 100k or 150k seems pretty surefire, being only 2 to 3 times a good year of donations.
6. Possible legal issues with kickstarter.
TL;DR
Volunteer Toady for 1 year development of playability patch using kickstarter money