Capital Games TeamConsider a split solution. Such as the delta only affecting damage received while on defense. And offense (not defense) only being boosted when on offense. Primarily thinking of GAC and TW, here. This would still give smaller teams a challenge when attacking larger opponents without being completely clobbered by the return damage.
Alternately, maybe unlock modifier slots for R9 characters that allow them to equip hard to obtain item(s) in order to tweak their offense, defense, other traits individually. Personal omegacrons; temporary or permanent.
Coding for this likely make things way more difficult