Folks,
Officers (Res and Reg) do much much more than deliver training - I think your discussion is a little one-sided. Piper, you make good points about what OCdts should and shouldn't do - for example, weapons, drill, etc - that's a no-no. In fact to expand on your point, officers should not be teaching very many subjects, particularly not to NCOs, during the course of a unit's training cycle.
However, one area that you are forgetting is that other, less-glamorous yet more important area that many officers find themselves employed in - administering the troops. I don't care if you are a combat arms officer, logistics, EME, Sigs, Mars, AERE, whatever - if you are an officer whose occupation deals with soldiers, sailors or air force troops you will get sucked into doing administration. No matter what kind of operational guru, "only a field guy", sea dog, whatever, you fancy yourself, at some times, the Admin Bell tolls for thee.
From what I've seen, most new Army officers arrive at their units well-trained to do their basic jobs by the various schools - tactics, replenishment, whatever it is. However, they arrive completely unaware of some of the back-end admin pieces they will have to know to take care of their people. That becomes a steep learning curve and one where Coy/Sqn/Bty 2ICs get to pull their hair out and do much much teaching to get the new officers' admin wired tight enough to take care of their troops.
When I was posted to a Res unit, I would have welcomed a couple civvy-u ROTP officer cadets parading with the unit - they could have learned a few things about the Army, they could have paraded when their class schedule permitted (ie coming in during the day to give the day staff a hand) and they could have been another couple fairly computer-literate, reasonably educated folks who could give a hand with the admin and learn a few things themselves that would stand them in good stead further in their careers.
There is more to service as an officer than just training and many ways in which, as a leader, you have to take care of your people outside of a field or operational setting.
My 2 cents.