I think your ideas are great (in theory)! However, I think a lot of what your suggesting may not be as awesome in practice. Mainly because GTA IV is a very buggy port to PC. So when a ton of things are spawned into the game often times you might have missing textures, script crashes, and a littany of other issues.
I would imagine some folks would be hesitant to help with this because of some of the other mods currently out there do a few of these things (VDH Policehelper for example) and from what I've heard there is a lot more in the works. I would suggest instead of trying to re-invent the wheel maybe just reach out to the folks who are producing quality mods and see if they would be able to take you under their wing and teach you some basic scripting stuff. Then, ultimately you would be able to produce your own mods?
Just an idea.... hope that helps.