> Gosh, I don't know, how about literally all of the problems that 2FA solves in the first place?

Well, it isn't solving this one. Option to opt out would be nice.

> aren't capable of keeping track of a physical device for more than N weeks?

Bit ignorant of you. They could be just plainly stolen by someone else. A piece of rag working as a tent doesn't exactly have best physical security...

> I'm not unsympathetic to the problems of the homeless ant the burdens 2FA entails, but I'm also not willing to ignore the huge problems the 2FA solves, and realizing there will often be a tradeoff between making it very difficult to hack into accounts and making it easy for people with mental and other problems access their accounts.

It's not either or.