I assume the door will be >6ft above the ground when on the gate... if that's correct, then I think you'd need means to assist evacuation from the emergency windows (as there is no wing there). Given this, I think a smaller door (739 style) will be better to be put where the emergency exit windows are, or maybe move it clear off the sponsons... as you need a slide from the exit and you don't want it to get poked by the wheelbay door or landing gear mechanism.
Anyways, nice stuff Keesje, although I was wondering if someone would do a mini Tu114 twin... *grin*