I'd leave it with Premier, it makes the coaster more unique, Premier coasters like that can't be found all over the world.
B&M would be nice, but would consist of Universal making a lot of things themlesves. B&M (maybe with the exception of the dive machine) tend to stick to the traditional method of going up the climb hill, going round the coaster and going back. ROTM requires a lot more than that, I can't imagine them making launches and turntables and stuff themelves, which would cause Universal to work more themleves ontop of themeing, ect they alreayd ahd to do.
Vekoma might have been good, but, again, Universal would have to give treatment. I don't think it's coincidence that's Disneys Vekomas are the only Vekomas I love. A Vekoma would've gone bad on ROTM's name anyway.
Intamin may have been alright, but I'm no0t a huge Intamin fan. Maybe a more intense launch, but I can't imagine Intamin getting away with having ROTM style cars, at least not with putting loads of pressure on the track.
S&S is debatable. They are really still in development with their launch coasters. Sure, Powder Keg seemed hugely successful, but I don't think that S&S could've tackled a project this big so early in their coaster manufactoring years. Then again, Premier Coaster aren't everywhere like I said earlier!
That's my theory anyway, so I'm glad Premier did it, it sets the standard for them