Portal abilities. IE: "Allies passing through your portal start regenerating hp (Xs cooldown, you can see the progress around the portal)"
"Enemy bullets passing through your portal have their damage reduced"
"Enemy destroying your inactive portal can't place portals for X seconds"
"You deal increased damage through your portal, but ememies see your outline through it (idk if the engine can support that)"
"Passing through your portal boosts momentum/launches players"
"For a short while after activating your portal, enemies see it as an allied portal"

Things like these would be so fun to have, although I don't know how they would be incorporated with the factions