I'm sure if they made it backwards and gave it an overhaul, they'd have to refurb the trains as well. So if they wanted to do it, I think they could pull it off quite well.
Look at what happened last time Six Flags ran a looper backwards:
the ride is a little boring, and going backwards is not much fun, although the ride is relatively smooth.
With the way everyone is talking about a backwards coaster, you might as well be begging for a Boomerang!