Plus, in canon, once he returned to his former power, he was able to break everyone out of Azkaban.

I would be rather surprised if, after all the characterization and buildup we've been given so far, MoR!Voldemort turned out to be capable of this as well.

It might not be a great idea to sacrifice the element of surprise by doing so, but still, if he already had a route to power even greater than he possessed before, I don't see why he'd stall on using it.

As a suggestion: he may have decided that his goals are better served by remaining in his current guise (which he presumably could not do if he regained his body) than by sheer magical power, at least for now.