Let me get everyone back into positions here.
Falconeye: You got a map idea (just the idea), but don't really know how to do it well. Don't worry, neither do I.
HappyTauren: You're right about the reason of this section. Here should be posts of idea's of how to make a map, not asking if people would like the map.
anderf: Please mind the language. We're here to post about the reason this thread has been made, not yelling at co-posters. And no: What HappyTauren posted as his first post was related to the reason for posting this thread.
Mechanical Man: Nothing needs to be said here, you're not in violation xD
Now what I suggest is:
You post your idea's on how you want to make this map, Falconeye. If you want people's opinion about if they would like to play the game, they should know how the game would work. Like anderf said: It's hard to make a game like GTA in Warcraft III. Remember the animations (not just shooting, but stealing cars and stuff too), the models (you can get a modeller for that), the triggers (going to be a lot of triggers to make it a worthy game), but most of all: The overall game experience. How are you planning to make people believe that this is GTA instead of Warcraft III? How do you plan to make them forget that they're playing a game based on dungeons, magic and ancient creatures, and actually think that they're playing a modern action game?
I'm not saying it's impossible, but it'll be a tough job. Major issue will be the camera positioning. If you can post your idea's for that here, people know what to expect, and give you a reliable answer, which is what you made this thread for instead of about 10 posts that don't actually are what you were looking for.