Eh, sure hope this ends up better then vice cry though. They just ran into some serious stability issues due to high poly models alone (not to mention a sh*tton of 3D grass).
Not really, we haven't. At least nothing that wouldn't be possible to fix. There were some problems, yes, but related to saving, since if I remember correctly, amount of displayed models was messing up savegames, and making them impossible to load. That was later fixed, thanks to Silent.
As for high poly models, they actually weren't much of a problem, and if Kov, the main creator of the mod, didn't decide to retire from modding, we could probably go on and on with the project, as we originally planned. I still have plenty of unused models, and have been modeling new ones after the release of Vice Cry 1.8, for some time. Geometry is not a big deal, and performance drops, related to 3D grass, for example, were limited with draw distances.
High resolution textures on the other hand, are a different story, and they've got the biggest impact on the game. Still, with proper organization of .img archives, everything worked in the end.
It's usually not stability issues and limits which kill projects - these, in definite most cases, can be fixed. It's the amount of work necessary to complete a mod, and extremely slow progress which overwhelm the modders. That's what happened to Vice Cry, and I sure hope won't happen to this project. I actually dig the idea of adding high quality elements to original Vice City cars, since HQ remakes, like Onepiece's beautiful work just doesn't fit the original game's style. I wasn't crazy enough to remake vehicle body textures in high definition (stopped at remaking liveries, logotypes and texts of all sorts), knowing how difficult and time consuming it would be. Your way of combining original models with new, hich poly additions could work. It can fail, if done improperly, without paying enough attention to the universal style, but there's a solid chance it could end up pretty well. Certainly worth a shot.
What are your plans for his mod? Do you want to recreate the entire city in high definition, or focus only on the "foreground" and most important models, either just for now, or completely? Could you share with us a basic checklist, or anything showing what you've done already and what's there to come? That'd be much welcomed.