Groom’s Mother as Moh?

A MOH isn't required. I would just not have a MOH rather than ask your future mother-in-law.

As long as you have a legal witness to sign the marriage certificate, a maid of honor and best man are not required. Do what works for you. If you are super close to her, then ask her. The only duty the maid of honor has is to purchase a dress of your choice, show up to support you and have fun at the reception. The rest is extra and not required.

I should probably add more details, my fiancés stepdad, brother, sister, and grandfather are all in the wedding party and at that point I’d kind of feel bad basically only leaving his mom out. We’re letting everyone know in advance that we’ll be covering all expenses so I’m really not trying to pin any extra financial duties on her, I just want her to feel as included as possible. I still can change one of the bridesmaids to MOH if y’all still think that would be a better option

Just don't have a MOH

You don't need a MOH. Choose people who are closest to you, not because you feel you "have" to fill every role.

View Quoted Comment Im sorry y’all but I’m really not asking whether or not I should have a MOH I’m just trying to figure out if I should ask future MIL or a bridesmaid.

View Quoted Comment Ask a close friend/bridesmaid. The mother of the groom already has an honored role in the wedding.

View Quoted Comment Thank you that is what I’ll do then, I’m sorry I really wasn’t trying to be rude in my last comment, it’s just kind of a weird situation and I want everyone we care about to feel as included as possible

View Quoted Comment Contrary to popular belief, people generally don’t get upset or feel left out if they are not included in the wedding party. Not everyone finds the added responsibility (financial/emotional, etc) to be enjoyable and prefer to be guests. Even if you cover all the expenses for them, many prefer to just sit back and have fun without having to work. Either way, you should not ask anyone to participate in the attendant roles before 6 months before the wedding as so many relationships and other dynamics will change before then.

Yes, It would be weird but I can't see why it would be impossible to ask.
" I wouldn’t want to ask her to take her focus off of her son that day.": This is not a valid reason to not ask her because the groom's sisters are often asked to be bridemaids and the bride's bros to be groomsmen. It'n not any different.