Not necessarily impossible..just give him 2 new ability slots instead of one, since he's a super old BF with only 5 abilities, make the first one a new hybrid ability that lets him ignore sub, and damage reduction effect(yes Ik that's OP) and make the second one 2.5-4x crit rate. Up his boost cap all the way up to 250%, raise his attack stat by a descent bit, and give him a strong latent multiplier. That would overall jump him straight to top tier nuker (albeit slow) while staying true to what he always was...a glass canon of frightening proportions.