Now, I'm wondering if the main character should know they're in the world of Infamous or just being a random person from that world who doesn't know anything. Because if they know they're in the world of infamous, then they're three main targets would be Cole, Desmond and The Beast. They might go after Nix and Sasha too.

Let them know also have them go after everyone delsin went after since there going to have blood and biomass powers they can use it to restore old cells and live forever they can also be there when delsin frees all the conduits also if you do have them copy delusions powers instead of making them weaker have them as strong a a prime conduits powers because delsins powers get weaker the more he gets as seen in his final battle 

Also when copying Cole's powers a cool karma bomb would be an EMP surprised they didn't use that in the game

Yeah truthfully he should be able to do more like emps, magnetic abilities, being able to enhance he strength and reactions to superhuman levels, turning into electricity for high speed movement, and so much more.