One thing I have been obsessed with is tomato bean soup. The recipe I base mine off is sopa tarasca, a Mexican dish that also uses a few ancho chiles. But you could use chile powder or omit that.
Anyways, I really like your idea of adding mushrooms and doing it in the pressure cooker. I might toss in a can of tomatoes and some onion and garlic. You could throw in other veggies too, like anything about to go bad. And add rice to really make it a meal. Beans and rice is so good when done right.