This doesnt sound much more different than "wiggling". You're still pressing a button (in contrast to tapping a direction) to get back to your neutral state. I suppose it would be a decent alternative, but it just seems about the same to me...=/Why don't we make it so you must press R once to get out of tumble, and then again to AD. That would delay it without you having to "wiggle", and new people would comprehend it better than having no AD, or having it come out after an unintuitive delay?
Also, wouldn't that possibly have an effect on teching as well should you exit hitstun earlier and try to FF and tech during tumble? I'm not too certain, but it sounds as though should you time the L/R input incorrectly, you'll end up in your neutral position on the ground instead of teching.