I know there was already kind of a post about the idea of playable flood. And I know a lot of people said its not possible because of the balance required and the overwhelming nature of the flood but. Humor me for a second.
Imagine starting the game as a pod or whatever in some far reaching corner of the map, slowly accumulating bio-mass (as a primary resource) and gaining units by sending infection forms and such to take over the units of other players? Of course yoy can produce some flood-specific units such as carriers. And in addition the longer your HQ exists flood corruption slowly spreads across the map, on which your units gain bonuses making them stronger and faster. So essentially all the floods power comes from merely existing on the map longer. I think it provides an interesting and unique challenge while keeping the Flood faction somewhat true to lore.