This is entirely down to your Discretion on accepting that member into your division. Technically, they do hold a higher ranking Superiority, but whether you allow them to control YOUR NPCs or your MEN's NPCs is entirely your choice.
Take my Division for example; The R.M.C, I've allowed all member units to control their own NPCs, whereas other Divisions may move the NPCs donated to the Division about, so other's have the chance to become stronger immediately; Even if the donated NPCs aren't theirs.
So at the end of the day, YOU as the Division Commander AND Founder has say on what happens. So someone with a higher rank entering your Division, well, they could possibly ask you to do things differently (give them a lease-hold over X-amount of NPCs you own), but like I said, it's your choice at the end of the day upon accepting these higher or lower ranking people into your Division.
If you accept someone at a joint command (Lieutenant like you) then you'd still have the prime power, being the founder of the Division, but either way, whoever you accept into your company is entirely down to your choice and Discretion.
But No, they can't take overall command of your division and yes, in a battle thread, they would be able to boss you about and take command of your men (giving orders). So it's your choice at the end of the day.
~Danny
Modded Deaths: 87 (Including Epic Battles) / Modded P.O.Ws/MIAs: 6 *YouTube Channel* Click if you dare...