Wave Skill for Legendary Marth

In order to make him the mixed-phase sword unit in my mixed team for story/annex quests, I'd like to give my L.Marth a wave skill but they are all 5* locked or useless or at least not optimal: Res by Aversa but he shouldn't face mages, and manaketes cannot retaliate against him, Def by Silas but my only 4* Silas is a +Atk-Spd so I better wait for another one

I think an offensive stat wave skill would be better, but do you think that it would be worth the sacrifice of Laevatein, Karla, Halloween Kagero or Loki? (though there's no way I could fodder her or Ishtar)