Collabs like this don't usually take off due to the scale you'll need here. Like some people before have asked, be a bit more specific with what you need, which style of artists etc and how you plan to run the city i.e. AI and the actual sandbox city itself.
If you post some kind of specification and details as to who you need in your first post insteadof just "I like GTA lets remake it!" then you'll get alot more offers. :)
I would help but i've got final exams soon :O
Good luck with it though, GTA is a lush game and I wanna see it recreated :)