Most designers design a plane (6-view), design the construction of the plane and the fit a engine and prop to it! The engineering feat of turning that process around would take more the the average bears tallents, I sure it could be do, be fun saying I have engine X and prop Y that creat nNN# of thrust, build the largest plane it could support. I think you would keep hitting stumble point! My designs when I start are real guesstaments as to weight, I usually look at like models if there are any and get a good estimate of weight and engine needs! Not being into electric motors i could not begin to help you there, but I have seen it discussed on this site. Someone will most likely chime in on that subject!