although I'm not entirely sure what it means in practice, in principle I like the idea of lieutenants. Certainly in the fiction there's a lot of stress placed on how good one's first lieutenant is, the bond between officer and the loyal subordinates, the chance for promoting one's protoges, etc. The biggest promotion, seemingly, was that from lieutenant to "commander". And later on we might have more "backstory," charting the admirals' rise all the way from the lowly rank of lieutenant

Also when we start using wave 2 ships, Lieutenants might be acceptable for commanding the small sloops (?)