I’ve just found that JBridge is finally available for Mac, and it’s a amazing soft to use 32 bits plugins in Nuendo 64 bits. In my initial tests, it works pretty well. No single crash and everything performs as expected, even with big problems. The best part is that it’s dirty cheap (in this stage), around 9 €.
So I finally moved my setup to 64, and it’s more stable than ever. The Steinberg’s solution is not as realiable, so I never felt too confident to use it in my everyday work.
I hope it helps.