I've made a few changes to our home that are more along the lines of Montessori traditions to see how Emmett would respond to them. I did these few things by spending about $3, but it definitely would have been possible without spending any money at all!
Firstly, I added a kitchen space for him, which includes snacks and water he can pour into his own cup. It's not complete yet because I need to put some "works" there too (basically Montessori-approved activities to keep him busy in the kitchen while he's in there.)
I also converted his crib to a toddler bed using a conversion kit we bought at the time we got the crib. It's low enough that Emmett can get in and out of it without assistance, though it isn't 100% Montessori approved. Three sides of the crib rails remain on the bed, which still kind of act like a "cage." Also, it's a dark wood color which is not supposed to be used (light colors only). It definitely still acts like a crib for the most part, but it's probably what I'm going to stick with, at least for a while.