When someone makes E-5 (Sgt) can that person request a different unit due to the fact they were a SPC prior with the same unit?

In general, it is recommended that you reassign someone when they become an NCO if you can. Many times, you don't have that option. It is a challenge for many people to go from being buddies to being their supervisor.

Since a BN Commander/CSM can promote to E6, they can manage them as well. Ultimately the CSM will need to decide. I have seen it go both ways, the problem would be in the form of familiarity. You are now an NCO, they (your buddies) know you too well, and that could be a problem if sending someone into harm's way. As a New Leader, you need to separate yourself to some degree from the troops. "The Loneliness of Command"...You love your troopers, but someday you may have to send them into battle and you may lose some of them (even if you do everything right).

I have mixed emotions on that issue. I can see staying in that same company as you already the chain of command and the troops you will be leading. But the chance of familiarity may be a difficult hurdle to clear.
In my opinion that would be the Commander and 1SG's decision. The simplest decision may be to .move that be SGT to another platoon in the company.

I have seen many promos from 4 fo 5. Never heard of anything like this before. If you are unable to function as an NCO n the same unit you are promoted in, then it's time to move on to another career.

In the past, company/battery level units have laterally transferred newly promoted NCOs to sister units in the same Bn for that reason. Nowadays, not so common. Once you put on those stripes, worry about making YOUR unit the best it can be. You will lose friends, but thats ok. You are there to lead, not lollygag.

Familiarity breeds contempt. Not always true but it is easier for the newly promoted to get a fresh start with a new unit.

Staying in that u it and having to learn how to adjust truly makes u better. You will quickly see who your true friends are and you will have to leave the rest behind. Learn from each and every situation and ask lots of questions because the Rank doesnt instantly make u smarter

Really, an E5 has no power to do shit in this army. They should make E5 the old spec5 tank from Vietnam. SMA is a pansy ass and is the problem with NCO's in today's ARMY

You can ask whatever you want. That doesn't mean you will get it, unless it is in a contract that was signed by the military. You are the military and the military is you, rules are rules.

Go for it. No guarantees, sometimes if your command is looking out for you, and they are able, they may make that determination whether you want it or not. If not you’re just going to have to step up. People do it all the time, when in charge, take charge.