Yes, I have. And no, no stats boosting abilities while leveling up should have been used either.
Geez... You're not supposed to do that for the Omega challange, though. It's just pointless to spend hours raising your stats like that when you just can use junctioning. The very point with the "no stats-effecting junctioning" is that you'll have a great stats dissadvantage.
And, yes... it IS possible. There's 2 ways to survive Medigo Flame, 2 ways to survive Terra Break.
Also, as for solo Omega, I've already done that too.

The only thing you really need to worry about is to time the GF summoning correctly before Omega uses Light Pillar.