1A.) Adding markers for players would be cool too. Then you could watch the President speed around, or check where you are relative to a car you're looking for.
1B.) I already suggested this and more
here. I'm not sure if the location example you give can be fixed, since I think it comes from the game itself. "Flint County" is just most of the map, except for Blueberry and a few other places.
2.) Fixing towing for tow trucks is pointless, since you might as well drive the vehicle you're towing. I'm OK with fixing the Packer, as long as it doesn't mess up the stunting possibilities that it was added for in some cases. I honestly don't think it would be very useful though. If the security and President are trapped, the more important part is getting the President out, not bringing enough vehicles for everyone. Securities should be sacrificial if it's better strategy.
As a side note, more people should use the Packers for stunting, particularly in LV. One security can drive it somewhere to be used for a stunt, then the President and the rest of the team can do the stunt, then the Packer is driven away before the terrorists can follow. There are two or three in LV in locations that would be good for this.
3.) It's cool, but I can't see it being used enough to be worth the effort. You can't shoot through the roof, and all the vehicles that would be candidates for such modification are so crappy that no one would want to use them anyway.
4.) Being able to transport a vehicle in the Andromeda or CargoBob would be really cool. I could see terrorists airdropping other terrorists with NRGs and combat shotguns with this.
5.) I like the idea of listing whether the President is in the air, water, or on land, and his direction. I don't like the invisibility idea. I could see this being used to hide how stunts are done.
6.) Kind of pointless. I'd rather have it as a command than a key for that reason, if it's added at all.