The Amarr breed the slaves themselves now, so it doesn’t make sense to only get them in Minmatar space. I don’t think you need unique resources for the empries to fight. The backstory is rich enough to feed to conflict.
As for why the empires would stop fighting, all you have to do is look at the Israel / Palestine conflict. They quiet down for a time, and then go back at it later.
If you want a more gameplay centric feature, you can take a look at the updated portion of this post, where I detail a way to get fast paced action into specific systems the ai generals guiding the factions choose.
There was also some fw discussion centered around pve here.