But the JA MP source won't contain enough of the SP code to deal with it correctly - wouldn't it be a rather incredible waste of personal resources to build it that way, as it would mostly be down to extreme trial and error, and could potential just plain not work?
1st of all: Unless I'm mistaken, Raven didn't release the source for SP for either JK2 or JKA. I'm sure it isn't in the SDK of either game, or at least not the ones found on JK2files.com. If I am mistaken, please let me know where to find that release. 2nd: If you want vehicles, JA is the way to go. You'll have a very difficult time trying to get a programmer to reinvent the wheel to get vehicles in JK2. The code just isn't there. He/she/it would have to start from scratch. 3rd: The programming part is a drop in the bucket compared to all the graphics and artwork and modeling and mapping that needs to be done to get something like this off the ground. If you get that part done, it won't be hard to recruit someone to build the game around it.
The worst problem: Find a coder
Hmm, so in which case wait for the Jk3 SP source? I've heard rumours of it. As it happens, I'll be doing the coding - It's what I do best ;)!