Yorpie

Oh my, Ford Explorers all over the place, I really don't like the sound of that. I'm not an American, but I've always seen the FCV as the main workhorse for the police, can't imagine all cops driving SUVs. Oh well, I'll just stick with sedans in the virtual world.

Sorry, I didn't read through the whole thread, but I want to share some discoveries I made nonetheless:
 
You're able to spawn any helicopter you want into the pursuit. I edited mine, so that when I'm at 5 Stars they spawn Buzzards with guns (Military), Buzzards without guns (SWAT), Savages (Military) and FIB Froggers (SWAT).
 
I couldn't for the hell of it get the Valkyrie or any chopper to work that would carry FIB personell. And the answer to the problem is quite simple. When the chopper spawns and flies in, the game continuously checks, wether the gunners in the back are able to fire at the player or not. If they're not, the helicopter will turn around and head off away from the player until it despawns. (I bet you have noticed before, how the police choppers fly away when you kill both gunners - same method). 
So in the case of the Valkyrie, the fact that both gunners have mounted miniguns in the back and cannot use their primary weapons makes the game always send the chopper away. In the case of FIB personell, I think it has to do with the loadout. In mine they equip pistols and smaller weapons  - when I replaced them for SWATs the helicopters started coming in. So it pretty much checks, if the gunners in the back have the ability to shoot and wether or not they have guns that can be used for such.  Maybe that'll help one or another.
 
 
 
 
Oh and one other thing: does someone know how to make the game spawn the police cruiser without a lightbar? There must be a file somewhere that tells the game which extras it can use. We'd simply have to add none to the list of possibilites to make the game spawn slicktops.