Pretty sure this can already be done by taking Officer Training as a skill and then removing it. Combined with Cybernetic augmentation, it can add up to a fairly beefy crop of officers. If you have the story points to do it.
One thing I would like is for mercenary officers to exist-semi permanently. That is, it would be nice if I could pick them up later after letting them go. Maybe just have them appear somewhat regularly at the planet you let them go? Or rotate between planets fairly regularly?