Give
this a try
It redirects all bottomprint calls into a queue (discarding any messages that are too similar to another already queued message) and then cycles through them
I haven't experimented with it using
actual bottomprint calling add-ons, so I don't know if the similarity factor needs to be adjusted at all.
But it works well with test calls
They still won't show both add-on message at the same time, but instead of fighting, all add-ons using the bottom print would be given an equal "share"
Probably the best you're going to get, unless you manage to get every add-on dev to work together with their bottomprints