It is an interesting, out-of-the-box, idea and it would make evacs a lot easier and faster. But, it would be a highly specialized piece of equipment. Like a self-propelled crane with an attachment on the end that can unclamp and lift the gondolas off the cable, then lower them to the ground. Something like that would really only work at the Disney gondola, since most gondolas don't have a service area under almost the entire length of the cable... so that being said, it would probably be quite expensive to develop and build for just this one gondola installation... But if they had a couple of them on-site, they could evacuate the entire line a whole lot faster.
Then again, stoppages that require actual evacs are supposed to be extremely rare, so the investment in developing and building it wouldn't be worth it.