I personally wouldn't recommend reclassing him. At level 15 he learns Dual Guard+, and that's a great time to permanently relegate him to a support partner.
If you want to reclass him anyway, most of his class options have good skills for him. General has Pavise, Paladin has Aegis, Wyvern Lord has Quick Burn and Swordbreaker while Griffon Rider has Lancebreaker and Deliverer. Take your pick of which of those you like, plus Luna they're all good skills (Dual Guard+ is a lot less good on a frontline unit but still okay. Quick Burn would likely be better though).
"When playing a game, the goal is to win, but it is the goal that is important, not the winning." -Reiner Knizia