If we’re rounding out the 2nd trilogy campaign, we got Nova. Add Stukov, and go into detail how he went from dead to infested, to uninfested, to infested again, and how he built up his forces and tech as we see it in Coop.
Perhaps Protoss could either be a Fenix or Alarak campaign.
The former on some “interior” missions where he’s in the digital world, hacking, cyberpunk like stuff. Gaining more Purifier AI champions (and even letting us use more than what’s offered in coop. Disruptor Champion anyone? )
The latter could be Alarak’s descent into becoming the highlord. He gets some VERY OP abilities, builds up a very might Death Fleet, but decides to hold back when it’s time for Coop for game play balance reasons