Very nice for liquidity, but what's the point of opening it up to everyone? If everyone has a market maker they will just trade each other or only one of them will take the trades right?

This means no profit for someone and a lot for someone else. Depends whose algorithm reacts faster. If it chooses randomly which account gets the trades, it will reduce profits massively while staying exposed to the same risk.

What really matters is the amount of money in the market maker. One whale could take care of the whole thing and make nice profits, makes more sense.

On another note, what other use-cases does the BEE/ENG token have?