Carapau, I don't think it's quite that simple. The overheating problem in heli motors which are over-geared has more to do with current than it does simple throttle application. In a SRH heli application, throttle is used to control rotor speed. If your pinion is too large, and you are using low throttle to keep the rotor at the right speed, the result is a huge current, even though the throttle is low.
In a fixed pitch situation like a multirotor, the load scales with the throttle application. So no ESC overheating should occur. 35% hover throttle is not at all uncommon.
Pumpkin: Biggest downside to a larger than necessary motor, is that it won't be efficient at lower loads. The exact same machine, with smaller motors, will actually fly longer.