Snipe is a beam and has a model like any other beam. You can't directly give Snipe a Yamato mssile because, well, it's not a beam. It is very possible to give Snipe a Yamato missile, but in all honesty you'd probably just be better off scrapping this whole idea and starting with the Yamato ability and working from there instead.
Wait, couldn't you use Jimmy's spell (Experimental rocket pod.) I think it shoots out a bolt of some kind, similar to a snipe. You could probably put it onto Nova, and then change the command card, make it level if you want. Unless if you're going for a Yamato blast that kills like a penetrator gun like jimmy's Sniper. I think you need to be more specific mate.