DarkBASIC Professional would work, but from the looks of it has no support for A.I, sound or GUI middleware. It has addons but they don't offer nearly the level of functionality or development speed. I also can't find any commercial or even finished games made with it and that's not good.
The Ethanon engine is unsupported and incomplete, and so can't be used. In this regard it's similiar to the XNA RPG maker http://www.youtube.com/watch?v=-Q6ISVaM5Ww http://www.youtube.com/watch?v=vtYvNEmmHXE
They look impressive though.
In regards to the engine. Here's a nice quote from a survey on choosing an engine.
"What factors do they use in deciding whether to license a game engine, and which one to choose?
The overwhelming favorites were of course cost and time. If we purchase a game engine, we want to spend less money and time than we would have creating the engine on our own. Otherwise why would we bother? In third position to money and time came genre relevancy, or making sure that the game engine works properly for the type of game you are creating. This emphasizes the importance of doing a thorough evaluation of any game engine you’re looking at, and knowing if a particular engine was already used for a game technologically similar to what you are planning to create (a first-person shooter, for example.) Also highly important to the responders was support and thorough documentation, a good-quality content pipeline, and the ability to easily integrate the game engine into one’s existing technology as well as with other middleware libraries."
Apart from a minimium graphical level ability which at this point in time is unknown. The engine also needs to have some linux or macosx support. A decent support network needs to exist in some form also. Those are the minimium requirements imo. Software support for GUI, A.I and sound middleware would speed up development but add to cost.
A bit more information about the Silent Storm engine. It's being used to make Jagged Alliance 3 now being worked on by bitcomposer a german developer, who has no major pc games to their name. But they did publish STALKER Call of Pripyat a post apocalyptic RPG/FPS shooter and were co-publishers of Jagged Alliance online, a web browser tactical MMORPG, currently now in beta stage. Strategy First is the canadian owner of the Jagged Alliance rights, and developer of many turn based strategy games. Everyone involved here would love to see Wasteland 2 get made, and be a success, so they may be receptive, and agree to let InXile piggyback on the development of Jagged Alliance 3, creating the required support network that's missing for the silent storm engine.
A open source possibility is the Ogre engine (+CEGUI), probably the most popular linux engine, and used in more than a few commercial games. Recently accepted again in Google Summer of Code, so still active as ever. Torchlight, a game was made with it in 11 months by a at least 14 member team. There's also the NeoAxis 3D Game Engine, which is based on Ogre and has a commercial team license at 1K. So this looks like a doable semi-open source alternative. Cube 2: Sauerbraten engine is also a possiblity, but less active but it has an official commercial version which provides support. In addition it has some inbuilt A.I functionality which may be useful. Though I can't find any commerical games released with it.
UFO Extraterrestrials is a turn based combat game and a total conversion may be possible. Not sure how much code can be salvaged, but the sequel for the game is due to be released this year. So the engine has support available. The developer is located in Czechovslovakia though. http://ufo.ufo-extraterrestrials.com/
Coming back to the Onyx engine, used in Dungeon Siege III. I remember Brian mentioning Feargus Urquhart CEO of Obsidian Entertainment accompanying him in his publisher pitches for Wasteland. So we can be sure him and his team will be asked about what engine they should use. And they happen to have built and own the Onyx engine (and recently announced they would be using it to make more games). This makes me think the Onyx engine is a prime contender as they will get a special deal and probably be able to hire a Onyx engine master programmer. http://www.youtube.com/watch?v=1Y4pOUQ8 ... r_embedded
The engines major problem is it probably doesn't support any A.I middleware, which if used will speed up A.I development for the turn based combat system.
If not Onyx my bet is on Gamebyro. It seems to have a faster content pipeline than Unity and better overall tools.
Going back to the graphics question. Fallout took at least three years and 4.2 million dollars to make. (adjusted for inflation) Wasteland 2 will have approx half the budget and half the development time. And don't forget the simplistic combat system in Fallout, Wasteland 2 is planning to have a far more complex combat system. So it will be a challenge to make a game that's half as long and half as pretty (in 2D), but just as good. So corners will need to be cut most definitely, and the only place where that's possible is in the art detail department. No talking heads and voicework like in Fallout is a good start, but not nearly enough. (voicework doesn't take much time too)
So if it's in 2D, background detail and 2D character detail and animations will need to be reduced compared to Fallout. I'm thinking the 2D art will start to look like something inbetween Command & Conquer: Red Alert released in 1996 and Fallout released in 1998.
But if it's done in 3D but the camera is always in a fixed isometric perspective, shortcuts can be taken, and the overall graphical quality would be at the Tomb Raider: Chronicles level http://www.youtube.com/watch?v=lNbFQJf3JTk
(the game engine was developed in 1996, this game released in 2000). But will look better due to the superior tools we have now for vegetation, lighting, shadow, particle effects and 'off the shelf' textures. And cause 3D objects just interact better with these new features.