One idea I like, but apparently nobody else does, as I have tried peddling it quite a few times with 0 success, is some sort of protective shield (insert right-sounding sciency term here) that activates when the damage to be received by the target exceeds a certain threshold, effectively stopping it (kind of like shields in Dune stop ballistic weapons). This would turn on its head the meta damage buff stacking.
Another is some active defense system that shoots down incoming grenades and rockets…