Having a "Power & Propulsion" specialized scientist at the beginning of the game, especially if he happens to have a high administrative level and research bonus, allows you to quickly outclass all the other aliens in terms of engine technology and easily defeat them. In another case, if you happen to get five scientists specialized at Logistics, there is no reason to keep playing, as every actually important research will take you few more years to complete and ruins all the fun after you had a game where you got decent scientists. I haven't found a way to add new scientists using SM mode and if you play legitimately, even with 10 military academies it might take you years to finally receive a PP scientist.
In short, PP scientists are incredibly rare, there's no way to get them reliably even if you use SM mode and they break your progress, making you overpowered. Please apply balance.