Anything specifically required, besides a bachelors degree, in order to transition branches and commission in the Army as an FA?

There's no guarantee what branch you'll get. You'll have to go to OCS, the Army doesn't do direct commissions except for JAG, chaplain, and medical.

Not that it esp. matters other than purely out of interest, I'd just wondered, how did you happen to settle on wanting FA? It's obviously fine, of course, certainly, I merely found your specific interest in that explicit branch interesting, that was all, if you might care to elaborate on that aspect at all...also, have you gone masters or Ph.D. level yet at all, or given any thought to that? I only ask, as, I can assure you as well, all services, for all warrants and commissioned, will virtually automatically insist on your getting, minimum, a masters, virtually from day one, trust me, been there, done that (BTDT)...as I'd said, you being USAF enlisted will obviously help you considerably, I'd just be most eager to hear more, as I found your specific question and preference of quite genuine interest, as I'd said, I hope all that was of use, if I find anything else I was thinking might be of similar interest, I'll try to send that, as well, OK?

https://en.wikipedia.org/wiki/Naval_Postgraduate_School

The same is true for this one for Navy...when I'd been in, my USAF CO O-6, he'd made O-7, I didn't know him at that point, had given me a recommend for my masters here, I couldn't get it, you might find their online Ph.D. in systems science of interest, it's the only one of its type I'd ever seen, as with AFIT, all warrants and/or commissioned can apply, senior enlisted, I'd only seen for USAF for AFIT, there was a YouTube video on that, NPS, I don't know if they allow it analogously, you'd probably have to do at least a couple of tours as Army commissioned to have a serious chance at either school, you wouldn't need to go interservice, Army can go to both, it's just that Army, aside from the command and general staff and war colleges, has, from what I'd seen, nothing analogous to AFIT and NPS, that was why I figured you might find knowing more of them of use and/or interest....

That is the single most limiting factor, but only one of a number of prerequisites. Talk to an Army recruiter. They can give you more answers on service to service transfers and commissions. Not many on here will be able to provide the current policies and procedures with much confidence.

https://en.wikipedia.org/wiki/Air_Force_Institute_of_Technology

Being USAF, you might've head of this school...if you go Army commissioned, you can, in fact, submit for it, all warrants and/or commissioned, as well as I'd seen a video for senior USAF enlisted getting their Ph.D.s there, I'm unsure about other service senior enlisted, can all submit for it, as well....

http://www.ocsfoundation.org

This, I've sent in numerous times, it's not all-inclusive, it doesn't include Army WOCS, as well as various indoc direct-commission programs, so-called OIS types, of which there are numerous, not just for the standard five services, but also for the USPHS and NOAA Commissioned Corps (the NOAA one is called BOTC)...the forum pages, I'd always found quite useful, there's a good deal of applicant stuff on them, I've looked through them in the past....

https://www.ocsalumni.org/

I just found this as well, it's apparently the site for the current Army OCS alumni association, I hadn't known it existed till I'd just found it, just now, I figured you might find it of interest as well....

I realize you're thinking you've given sufficient info, as with a good many other similar threads on such things I've seen, however, please trust me, for all of us to help you adequately, we really would benefit, as would you, from knowing more. About the whole FA thing, I get that; however, you've given nothing as to assocs and/or bach major(s), grades, GPAs, explicit coursework titles, hobbies, interests, incl reading types, as well as sports, esp. martial arts, all of which would be quite useful to try to be able to help you in trying to go in such a route. Also, you might possibly find of interest to know that, before the present single Army active-duty OCS, apart from the ARNG OCS programs, Army had an actual separate FA OCS program I'd sent stuff in on before, as my late father-in-law, who was lost long before I met my wife, had actually gone through it during WW2, it existed at least through Vietnam, I'll try to send you the alumni association link for it, the program was at Ft. Sill, OK. His VA headstone had been, we'd found, missing his Bronze Star, which we managed to have added, along with getting a combat "V" added as well. That needed a good deal of approval stuff to actually, finally get, not the BSM, that had already been approved, I'm speaking of the "V", as the "V" was only created after WW2 ended, in 12/45, so, for that reason, we had to actually petition NPRC in St. Louis, as well as the VA cemetery where his headstone is; NPRC had to petition Army, we also had to go to Congress House offices, as well. Finally, Army approved sending us "V" devices, even though that oddity to the law existed, so, amazingly, VA and NPRC were quite helpful in getting us an exception to have the "V" be approved to eventually be added to his headstone, as the actual general orders with his citation were actually found, listing his having gone through a minefield to rejoin his unit, during the Battle of Nancy in France, during the crossing of the Moselle River into Germany, by his unit, the 90th Div., the Tough Hombres, at a small city called Petite Hettange, in France, which I did in fact look up, just out of curiosity. My wife and I would love, obviously, to be able to go to one of the D-Day reunions, if we might be able, if only for that reason; apparently, he'd also exposed himself to quite considerable German fire, as he had to go out in the open to direct artillery fire into the town during the whole thing; we'd never quite understood his whole story, though my mother-in-law, who's 96 now, actually kept the penciled, handwritten citation by his Lt. Col. from the whole engagement, I just figured you might find such history of interest, being as you want that branch, apparently, most generally don't realize any longer that separate Army FA OCS existed, I'll send you some other stuff, you might also similarly find of comparable interest and/or use. Trust me, take the time to actually do a detailed biosketch, with all I'd mentioned, or as much as you possibly might have time for, and/or see fit to include, it's be a real help, as I'd said, in trying to give you suggestions. Further, I'd been Army ROTC for 3 yrs., the last two on scholarship, I never got to finish the program, I'd gone USAF OTS instead when it'd been at Lackland, it's at Maxwell now; while I'd been there, many others in the program, I actually had to go through it twice, I got recycled the first time through, had been prior enlisted in other services, one guy actually had Navy enlisted sub dolphins on his USAF shirt, the only time I ever saw that, you know? Let me send this, then I'll try to send the rest, OK? If you look through the site here, you might see the stuff I'd sent in about the Bronze Star and "V" on my late father-in-law, it was a couple of weeks ago, so it should still be reasonably visible, I should think; hope that was of at least some interest, at any rate, OK?

SrA (Join to see) start here
https://www.goarmy.com/careers-and-jobs/browse-career-and-job-categories/combat/field-artillery-officer.html

ROTC or OCS.