Here are some of my ideas
I know there already is robbery in progress which basically is a carjacking. But what about armed robbery's? It should be like this:
Three locations: The Museum, the lawyers office, the bank. If anybody knows more you can always add. At the museum and lawyers office there should be 6 - 10 suspects. The suspects should be the skins of Packie, Michael and Derrick with their balaclava's and ak - 47s. At the bank there should be 4 suspects, with maybe 1 or 2 outside shooting at the police and two inside. Again with the bank robber skins and the ak47s.
As the title says, two different gangs shooting at eachother like Chinese vs Gangsters or something like that. There should be 4 - 12 suspects with maybe a vehicle for each gang to take cover behind. They should have all kind of weapons: pistols, mirco uzis, shotguns, ak 47s, molotovs. And offcoarse, they should be shooting at eachother.
There are already a lot of chases with this mod but how about one that doesn't start with you, like you receive a call from an officer in pursuit of a suspect and he needs help, like you sometimes call for backup during a chase. When you arive there should be 1 - 2 police cars chasing a vehicle.
A police chase mod in San Andreas I remember had the ability to call in roadblocks, so why couldn't this be possible with IV? I was thinking of when you press a button (Numpad - is spike strip, so why not use Numpad + for the roadblock) you will request a roadblock and a few 100 metres further a bunch of police cars gather to block the road. 2 - 4, depends on how wide the road is. And maybe add some signs to, like the police use in the roadblocks when you are on the run with 3 star wanted level or higher. I wouldn't add officers on foot at the roadblock because they would probably shoot up the suspects vehicle immediantly.
Pressing F3 5 times will result in 5 police vehicles (the two police vehicles, noose cruiser, noose patriot) responding to your location. Pushing the button a 6th time results in a NOOSE team showing up in a Black Enforcer. How about when you push the button a 7th time another NOOSE team appears and the 8th time a FBI team comes.
When you have a suspect in custody and you request a transport because you are to lazy to bring him to the police station yourself, a police car shows up after a while and the suspect gets in. Would it be cooler if instead a Prison Transport appears? Its just an idea but I think it could be nice. And maybe one of the officers gets out, comes towards the suspect and points a gun at him so the suspect walks and gets in the transport (a bit like police officers lead suspects to police vehicles at gunpoint after they got captured after a foot pursuit.)
IMPROVED OFFICER NEEDS ASSISTANCE DIFFICULTY
I would like to see the difficulty of the officer needs assistance mission a bit harder. When I arrive at such a callout the police officer kills the suspect and the mission is over, so basically he didn't need any backup in my opinion. maybe the officer should be behind his vehicle under fire or being attacked by 2 drunk guys in a fist fight.
I've seen a mod which made a firetruck show up when a vehicle is on fire and exthinguis it with is water cannon. It would be cool when you push the F12 button, a fire truck is requested and on route and when it arrives it exthinguishes any nearby fires.
NOOSE TRUCK AND INMATE TRANSPORT
When you request a vehicle to patrol in you get to choose between the police cruiser, police patrol, noose cruiser, noose patriot, fib buffalo. I think adding the noose truck (enforcer) and the inmate transport (police stockade) would be nice. Maybe with another button though becuase sometimes it already is anoying you need to press the numpad 7 button ten times before you get the vehicle you desire.
M4 AND COMBAT SHOTGUN FOR NOOSE AND DESERT EAGLE AND MP5 FOR FIB
Switching skins is cool but when I change to NOOSE or FIB officer I think I should have a bigger weapon than a pistol. So having an M4 or Combat Shotgun when you change in one of them would be cool.
These are just idea's and suggestions, do with them what you want, this mod rules anywayz :P