I’ve never done one but talking from people who have, Vmcg, Vmca and V1/V2 can be quite different to normal, especially on a heavy, sometimes leading to an awkward gap during takeoff where the options are very limited. For us it used to be volunteer managers/trainers only, given the risk exposure. I think on a long runway at sea level it probably works but add in a bit of WAT and things get complicated.