You can try to add max shot time constraints to target not having First/High priority, for example slot of 1 hour. This will spread data on more target and popup the First/High target in execution.
Anyway like I said more scheduler will come, one for HA. And the Skip Ahead priority.
All the best
Leonardo
This will never possible, constraints are for target and not for filters.
I just write this post, probably can help on some way: