3D games make me think, is this OGL or Direct3D? And if your 3D engine is only a renderer, it'd be better create one yourself, it doesn't even take time, I have one made already (and it isn't only a renderer)
Anyways, this isn't going to be less than atleast 400MB which I guess, I won't spend for a game like this. I don't think the idea is too great for a game, play some GTA or stuff, I'll prefer those games to this, and obviously there is no reason except that you havn't said that there is anything special in this except that it is 3D.
It will be so easy to hack this up, you'd be having models in a file, textures in a file and etc., I could mess your game in a matter of minutes.
Take what I said seriously, this needs better features AND A STORYLINE, don't make this end up like Pokemon PC.
EDIT: IT's only been a week since the last post, can't you guys wait?