The way you describe him, Zenyatta would definitely be appable.

Our only hard rule on appability is that "characters with a canon base must have enough canon for the applicant to write a cohesive personality for them without having to rely on headcanon". There are no hard requirements on anything else, so a few sentences of canon when it comes to history will be sufficient! Just pad it out with headcanon that is in line with what canon supplies you with.