As stated is jax the most versatile champ buildwise?

Not really, since he is forced to get a triforce and the gunblade thingy

Jax can build lots of diffrent items and no. he is not just restricted to triforce and gunblade. I personally rarely use gunblade on jax. And in season 3 the triforce is incredibly expensive. Jax can be built as ad or hybrid bruiser. Or as a striaght tank as his e and ult have exceptionally good defensive qualitys. Jax has alot of diffrent builds etc. But you can't say he is THE most versatile as there is no such champ. All champs are diffrent and can be built in many ways. But from a jax expert such as my self with over 200 ranked games as him. I would say he can be built in many diffrent ways because he scales in to late game so well.

I'd say Kayle is pretty much as versatile as he is, but yeah, he's pretty much one of the (if not the) most versatile champion in the league.