Should I begin a Valter merge project?

If you like the unit why not. Preference over meta any day

Sure. Don't see why not. Just know that Valter is a GHB unit iirc, so you won't be getting a +10 merge of him anytime soon.

Only issure is that he is one of the three units with the coveted Panic Ploy. Zelgius, the second, is so good that he's hard to give up, while the third option, Luke, hasn't appeared since his introduction last June... when his Red focus was shared with 2 other units. Ouch.