In the vein of a macro mechanic for Rebels, something I have been thinking about is an ability that would make units tougher as they lost models. An obvious issue here is that it wouldn't make characters better, but those aren't exactly the problem with Rebels. The Mark II would also be excluded, and that thing definitely needs some sort of buff, but that's another issue.
Anyway, maybe something that lets the Rebel player roll 1 additional defense die per model lost from the unit. So a naked Rebel Trooper unit down to the unit leader would get to roll 3 additional dice while defending. This has the added benefit of giving Rebel players an incentive to take personnel upgrades in their Corps units, as a maxed out unit down to the unit leader would roll 5 additional defense dice. However, this might be too good, as it would make Rebel trooper units very difficult to kill without large attack pools. Maybe if the bonus dice were reduced 1:1 by Suppression so they could be worn down with multiple attacks? This would also prevent the ability from stacking with Danger Sense. I would also have this not apply to Mandalorian Resistance/Clan Wren or Creature Troopers, and maybe not Wookies either (and give them some other sort of buff) just for flavor.