Good luck bud

Agreed

Husband:
-provides income
-owns house
-takes care of someone elses kids

Wife:
-guilts him into giving up his passion project with an false "either or" premiss

Watch “Throw Momma from the Train” with the wife.

Build her a MIL Cave. If you have the space, you already have the talent.
Be a Hero and make them happy.
Then when momma passes the Wife can have a cave of her own.

Her kids can share a room so that her Mom can have a room.

Well rich soon to be stepdon. Build an extention for mil. Like a treehouse!
Provider for all, work harder not smarter, arange for MIL to cach Covid the gigalo!

What will probably happen is the wife will either get her own way and you'll lose your man cave, or she'll divorce you and you'll lose it anyway.

Wrong wife.

Your wife is being egged on by her mother for sure. Which means you’re right that when she moves in it won’t be the end of you having to compromise. Having her in the house is big deal and I can’t see it ending well for you, no matter which room she ends up in.

She's the asshole, but whatever happens, he has already lost.