D3D and software modes will not be done simply because they are far too much work to make the game playable for a very small minority of people who won't update their computers. I'll probably be doing some kind of selection/info screen eventually. 3rd person would be a novelty feature that I doubt anybody would actually make use of much, so if I do implement it, it'll be a long time down the road when there's nothing else to do.
As for the quake3 engine, this game is too far into development to switch engines now, and considering how very slight changes upset some people because it didn't "feel" the same, moving over to an entirely different engine I'm sure would displease many people. The visual quality is already about the same, if not better than Q3, so there's not really any point. If there are any specific features that Quake3 has that paintball2 does not, I can port them over.