Thank you @abu_shafi for suggesting a solution here! I've copy and pasted your Comment here as an Answer for visibility:
"Target works on single priority levels and you can not change the priority on runtime
as you mention you already have Pega and NBA you should use that for refining audience segmentation
Other way to look into is adobe campaign where campaign priority can be chained and changes on runtime
Adobe Campaign has its limitation as this is not intend for realtime and it runs as batch and its for outbound not for inbound
But we run a POC with Adobe to prove that this can be done and performance can be achieved
Thanks
Abu"