... it makes sense to draw from the Ultimates stuff, that was largely where I'd heard all of the chars took their inspiration.
So, there are bits of character inspiration and plot that come from Ultimates, but "largely"? No. The Ultimates are Millar's work - and Millar's basic approach to comics is that every character is actually a jackhole. Millar doesn't seem to believe you can have superpowers and be a fundamentally good person, I think.
I mean... Ultimates Hulk is a cannibal, and kidnaps women to be his concubines.