Introduces new tier based mixed groups of cops, where it makes sense
on Very Hard the beginning of heists will have more local swats and closer to the middle and end of the heist there will be more FBI (indicating the FBI is taking charge) there will still be some locals, on MH the FBI will spawn more near the beginning while Gensec starts to take over.
Does :

• make Very Hard and Mayhem a little more interesting
• make the Housewarming groups make a little more sense without straying very far from their original design
• add shotgunners back on its own

Doesn't :

• trivialize Death Sentence
• mix tiers into the same group
• bake a cake