Hate to be the one to disagree, but I think it's one of the easiest investments a young chassan or kallah can make in the relationship with their in-laws (ETA: and spouse). I'm pretty sure parents in law typically appreciate it. It may feel awkward the first few times, but you get used to it quickly enough.
It also helps in talking to your spouse about their parents- I don't think "your mother said" sounds quite as nice as "mommy said", etc. It puts you and your spouse on the same team with the same sets of parents.
/.02
גם אני מצטרף להנ"ל. Definitely felt awkward in the beginning, but no less awkward than the other choices. And my in-laws are always around, so most of the avoidance type options kinda break down in the long run.
I think my general rule is that when I'm having a conversation with anyone on my wife's side (including my wife) about anyone else on that side, I call them what the person I'm talking to calls them. Which is why it's funny that this one hits different:
To my wife's sibling's spouse: Awkward fumbling while saying "Mommy/Ma"
Some how with my sibling's spouses it's totally fine - maybe it helps that I don't think any of them call their parents the same way I and my siblings call mine. But with my wife's siblings-in-law it just doesn't work for whatever reason.
How’s she supposed to know which “mommy” you’re referring to ?
Definitely think it changes the equation if you and your spouse both call your mothers the same way. This is a (different but similar) more common problem by grandparents that in my family is solved by a whole mishmash of terms.
Not now GPT, not now
This is interesting to me for 2 reasons. First of all, because 'first name' is probably the least common option for frum Jews, and yet it's gotta be one of the most common options for the average American. But also because of the fact that 'mother-in-law' is dismissed as to formal, yet somehow shvigger doesn't feel that way at all.