In this AU, Ed keeps both his automail arm and alchemy, because he spent his entire childhood learning it, and although he is a smart dude, it...I want him to keep it 

(after some thought, because their gates were connected, when ed gave his up, he had been able to use al's gate, so they both are able to use alchemy) 

So perhaps truth just let him trade his arm for his brother because reasons

As for my ships, i have: 

- Al X May, because they are both (in my mind) wholesome and good people, who deserve love and affection and happiness. Just 2 pure (mostly) beans who are perfect for each other. Although May can be a bit of a spitfire and al does occasionally does things that remind you exactly who hes related to (ed). This is my OTP

- Ed X Winry, this is canon, Winry gibs ed all the love and support he needs/wants, and Ed would anything to make sure that Winry is happy and safe and all that. And although Ed doesn't really say that he appreciates her (he does) Winry knows. Although it is canon in the epilogue that they have 2 children, I can imagine that Ed would probably want more kiddos (he seems like the kind of guy who'd love children, and would gib them affection, although he won't be as bad as maes, he won't be too much better than him). Also, i really like the idea of this ship, but genderbent, mostly because Ed throwing hands with people over twice his size and winning, will be 10000x funnier if it were fem!Ed, and male Winry because they'll have children, and it'd be kind difficult to for 2 women to have bio children (ed being trans dude is also great) 

- Roy X Riza, because they'll follow each other into hell and back, would fight to the death to  protect each other, and if one were to die, the other might just give up. There really is nobody else for them but each other. (found family with dad mustang and mom riza is fantastic, with either just the elric brothers as the kids, or perhaps the mustang squad as the kids, great either way) 

- Ling X Lan Fan, Lan Fan was willing to give up her arm to help Ling escape with their lives from a battle, after offering up her own life ofc so that Ling could escape easier, but Ling would never have just left her to die. Lan Fan would do anything to protect Ling, and he cares deeply for her, and fights along her side when in battle (they are technically prince and bodyguard, but like hell is Ling going to stay on the side lines) 

These are my 4 favorite ships, and although they're all hetero, they are quite perfect for each other. 

Heres what happened after the promised day, as per my headcanons, everyone gets a happy ending because im in a good mood

After the promised day, Al and May would probably travel to Xing (well, May would return shortly after, and Al would go visit her once he's recovered) with Jerso (fish/frog/slime chimera) and Zampano (pig/boar/whatever chimera) as per canon. But tbh its would mostly be May teaching Al alkhestry, and Al teaching May alchemy and then the both of the travelling across Xing and the other eastern countries on that side of the desert to study their alchemy/alkhestry, and they are just having the best of times because they are together and they deserve each other. 

Win would probably stay in her home town (that I can't spell) and be the town automail mechanic/doctor (no idea if she were, but her parents are doctors, and she does have medical knowledge, and it is a small hic town in the middle of nowhere) and Ed, as per canon, would travel out to the western countries to learn and study their alchemy (and get into trouble/fights because hes ed, but much less than he used to because 1. hes not very short anymore and 2. hes matured a bit and now has a longer fuse) And chances are at some point pinako will be the only town doctor after Ed breaks his automail again and winry has to go fix it. And although Ed would study alchemy, win would probably study medicine/automail stuff, and probably end up helping/treating the occasional sick/injured person because she can. Mostly because why not learn while travelling with Ed who is studying alchemy.

After a few years of travelling, Ed and Al (and may) meet back up in amestris, where they combine their knowledge and teach each other the things they've learned, after which, they'll probably settle down somewhere and start up a school or something (the Elric school of alchemy and alkhestry) the school nurse is probably Winry

After a about a year or 2, fuhrer Grumman will retire, leave Roy as his successor and Riza a queen, (Grumman will mostly be dealing with and fixing up the messes from the promised day, and perhaps changing some laws so that Roy and Riza can be together) and not too long after that, they overlook the country transitioning into a democracy, (with roy having been elected for the first term, and then not running again afterwards because it might not be much of a democracy if the same people keep getting elected) After which, he'll probably keep overseeing the isvhal restoration (which will probably take a few lifetimes tbh, but hes glad to do what he can) 

Ed can say he has insulted the leaders of 2 countries to their faces (Roy and Ling) and theres not many people who can say that

Ling will become the emperor of Xing, and Although he would get a harem, he just can't imagine he'll be happy with anyone but Lan Fan, and really doesn't feel anything for any other woman, so he might abolish that. He (and Roy) will do a lot to improve the relations between their countries, even perhaps building a railway between them so to make crossing the desert easier. He will also improve the relations between the other clans (mostly between the Yao and Chang) and often pushes for unity rather than division in Xing, and perhaps set up a few inter-clan organizations and the like, to further encourage cooperation. 

Our good girl rose will learn to move on, be an upstanding citizen of her town, and one day, she might just find someone (that hopefully won't die) she is also wholesome person who deserves happiness.