Alright, here's my idea

When choosing items to send with a lioness, there's an option to send an additional 15sb to check her cub amount. If the request is accepted, the sb is automatically used and shows both the lioness owner and pms the heat requester how many cubs the lioness will have.
Pretty simple :)

Just so the heat requester can know how many cubs to expect and clear out territory space/broodmother protection slots accordingly