Legendary attribute is cool, but ultimately not as good as Immunity, IME. You can always create a rote to give you better soak - or to decrease your odds of being hit altogether (caveat: I have a personal preference for high Dex over high Stam, just because it gives you better initiative. Um).
As for the Paradox thing... I don't
think there's any errata for that? I mean, obviously everything is subject to approval, and the ST can always say no, but it couldn't hurt to ask, I suppose. I actually did let the player take that once, with the condition that I gave him a secret flaw*: he was a Marauder, and
nobody with less than... gah, it's been forever, I think it was less than seven Arete and five dots of Mind? Was able to figure it out.
So all of his Paradox backlash hit the other characters. So while everyone was patting each other on the back, because they had a party member 'immune' to Paradox, who could do some awesome blatant stuff when they needed it done, well...
Alas, the game fell apart before it came to a proper conclusion, and I wonder to this day how that would have gone...
The moral of the story is: Be careful what you wish for, your ST might be a Literal Genie.
*I also gave him seven freebies for it, and he was so ecstatic that he never looked further than beefing up his Force and Prime spheres.