If 15 queens, in this hypothetical, then you have more than enough to put a few extra injects stacked up on your hatcheries. Sure that isn’t optimal but at some point you are fighting a losing battle of efficiency.
queen is important in the early game. Making changes to divide queen’s tasks is not easy.
yes that would be nice, but fair it is zerg macro cycle. other races switch buildings for production, build buildings. → zerg spams inject + creep.
therefore both sides must be “equally” busy.