The policemen sitting in the helicopter can shoot!

I like the idea of at least trying it and seeing how it works, if it's even possible. Might be too OP but if it was limited to some guns maybe...
If you mean Like single player helicopters then thats what seasparrow is there for.
You can attach platforms to police Mavericks but that would be more useless and an easy target unless the helicoptet Will have 2000hp and the gunners reduction from bullets.
Nobody can escape their sins, everyone gets punished whether it takes a day or an eternity.
You can change who you are, but you cannot run from yourself.
It is relevant to mention that the /rappel /abseil commands exist to allow groups of law enforcement to get the drop on criminals.

Not sure how useful this actually is though since I've yet to see people do it (though I am sure I will find a find to try it out with me sometime).

Not an inherently bad idea but not really sure what this would change as a whole given you need to be on-foot to perform an arrest.

Decided not to rate since I'm indifferent.
Not possible