In the sticky referenced in post #2 above (which started in 2008 and is 28 pages long, by the way - not the easiest thread to navigate), they talk about what happens if you tag your bags, skip the bus and go right to the resort via cab, rented car, Uber, limo, etc and then for some reason, the bag doesn't show up. That seems to be the only concern because when you call Disney, they can say "we have no record of you being on the bus" and you could be in trouble. The OP's suggestion of tapping your band then getting out of line, may alleviate that concern? Curious what others think.
Also, MDE is right near the rental car counters, so I don't see it as a big hassle to do this and the advantage is not having to haul your big checked bag(s) in your rented car - especially if you have a big party and a small/midsize car.