Got your attention didn't I? Yes I'm serious. I just had some inspiration this evening after accidentally getting a tape way too loose and unable to move it because it wasn't on a taping panel. (and wasn't a 2-chance tape)
So I thought what the heck, lets see if a hair dryer will loosen the adhesive enough to get the tape off without tearing the diaper. And by golly it works. Put the hair dryer on low speed hot, and hold it about 3" from the tape, while gently pulling to peel it off, as much as you can without starting to stretch the material it's stuck to. After 5-10 sec you should start to get it moving. Go slow. Takes about 15-20 sec total to peel off the tape.
Some of the adhesive will be left on the diaper where the tape was, so this works better for tightening things because you'll be overlapping the sticky spot you've created. The tape may not stick as well as it did before, but it works good enough.
Keep an eye on the tape till you stick it back down, don't let it touch anything, even its regular backing. It'll be crazy sticky with the adhesive warmed up like that, it's like warm gum.