I was unable to save my edited customized CAS to my unique tab. Yes, you can only share 1 CAS at a time. I'm getting no luck getting a match, so I can't try a customized online.
I'm pretty sure I have your Siegfried on xbox (middle of the map in the u.s.). Had to snag him so I could unlock your mysteries. Haven't tried to see if he's locked out online. I wish there was a better way to find CAS. But there are some creative people out there.