It's going to sound pithy and I'm not a software developer (so fuck me if I'm wrong), but at a certain point they should just be able to brute force emulators for PS1 and PS2. There's enough power in the fucking thing. Just do it and let people either use their discs and/or talk to the damn publishers and put entire catalogs up for sale.
Like, I kinda get (in a cynical way) how many HD remasters there have been. The last generation dragged on so long I'm sure tons of games were made with some high-res assets. That, and they can do a quick port job and get double dippers.
But 15+year old hardware? Just do it. Build that shit in to the OS FFS.