I wasn't actually trolling, just curious if any ASCII purists would declare a Fatma or something to see a DF-inspired '3D' game.
Mainly I specified HL2 since there is a very large, multiplayer modding community with freely available models, especially through Garry's mod. Also HL2 is pretty cheap, was a best seller, and goes on sale regularly so it'd be pretty affordable for new players to get ahold of the mod. I also wasn't thinking an absolute fidelity, Toady's stamp of approval, kind of port. Really just something inspired by DF fortress mode.
Also it would be multiplayer and team-based, mainly open-ended, team vs. environment or objective-based. Though a further development might be goblins vs. dwarves.
I think the main technical constraints of Rogue-likes in a 3D engine are:
1. procedural generation of levels (can Source support that?)
2. can levels be remapped durring play like Dwarf Fortress? E.g. Digging would violate a room definition (i.e. 'brush' if you know Hammer, the HL2 mapping program). Could Source remap a room during play, without crashing?
3. Maximum number of players and character models that the game could support, since a primary game goal is to increase population.
Content-issues, props, would be less of a problem, and much less so if the game-play were low-fidelity inspired. E.g only one type of workshop with a skill system, instead of a dozen of workshops.
Turn-based wouldn't be a problem because it would be FPS and also RTS-like. There already are successful HL2 RTS-FPS hybrids, and those would be a good template for the mod. Players would be the individual works, with perhaps a mayor giving orders and coordinating with the team, but without absolute control over the players. A leader with a good strategy can still lose, thanks to an uncooperative team of dwarves.
Dwarf Fortress-like interface issues wouldn't be a problem mostly, since any AI bots would be window-dressing, not to give orders to. Rather the team of players would do the real work. A HUD-like system where a 'mayor' communicates with the team by designations would be possible. Again, I've seen it successfully executed in RTS-FPS hybrid mods.
Mapping-wise, DF2 is rectilinear, so that would be a fit with HL2 mapping. And the mod could keep to a subterranean theme if outdoors mapping couldn't be done nicely, but I know it can be done somewhat decently from the RTS-FPS hybrid mods.
If you're curious about what I mean by a RTS-FPS hybrid mod of HL2, examine this:
http://www.empiresmod.com/