Well, one of the first things I do in a new game is building a few more academies. As all officers, including scientists, are trained in academies, this resolves that kind of problems over a couple of years. Until this happens, I just roleplay the shortage in fields I don´t have scientists in. If, for example, I don´t have a missile/kinetics expert, my fleet will start out with lasers or particle beams and no missiles, gauss or railguns, pretenting that that kind of things never even crossed their minds.
Power/propulsion or defese can´t be ignored, of course, but research in those fields is then conducted by what scientists I have and only the absolutely necessary stuff.
Limiting yourself in that way can give you a very interesting game.