For armors, Aeneas is an easy choice. But also Mirror or even Gaea's can work.
Top Accessories are likely King's Amulet, or even two of the Boots, Divine(more base mobility) and Spirit(can retreat after combat). Winged Shin Guards will be a nice one as well.
Scarlet Reaper and Throne Guardian are nice for him in terms of weapons. For once he doesn't want Ragnarok since it doesn't work on AoE, Blue Star doesn't work for the same reason. Yggdrasil Branch is usable if you want him to be tankier. Ironically he'd be the only unit that actually wants Broken Star if he could wield it.>Heart Bond passives: When forced into battle, magic damage taken-10%. & When forced into battle by a melee attack, damage dealt+10%.
He seems like a very fun unit, definitely SSR tier like they said they wanted for SP classes. It's still below what SSRs get for equal heavy investment, which is the entire problem of "low rarity" units to begin with.