If a multi-agent game is played in which each agent grows proportionally to its current size, isn't the end result that small agents are eaten by big agents, and at the end you have one big agent? Ie the end state of Monopoly? In practice, systems crack apart by the time there's only a few agents left.

But it must be a wild ride to live while these cracks start to show. It probably looks like the greatest living mathematician making stream of thought tweets about how there aren't any small agents left.