Arnold could have played a good Mr. Freeze with a good script and direction (although it still might have seemed a stretch) but he could have played a good Bane with even a decent script (one much better than that actually used but still).
Re-reading the Knightfall comics Bane seems pretty inspired by both Arnold and Dolph Lundgren.
When Arnold was first cast in the film I assumed he'd be playing Bane.
When I found out he wasn't playing Bane I wondered how they'd make Bane look so large standing next to Arnie.
Clinton/Kaine 2016
Unfortunately Arnie was at the end of his heyday at the time.
Him as Bane would've been like Stallone as Judge Dredd unmasked all the time due to him being such a huge star.
I've always argued this. Schwarzenegger isn't a bad actor, he's only as good as his director. Working with Cameron or Verhoeven, he can turn out a great performance. But give him to Joel Schumacher, and he'll do what Schumacher says.
100 Greatest Action Movies - http://www.imdb.com/list/ls000708268/