Quite easily, they could release an update that recognizes PS1, PS2 and PS3 games but when you insert the disc it loads up PS Now and plays the game for free. Achieves the goal. DRM acceptable. The only downside is there is no guarantee that a. Sony will put the game on PS Now and b. what happens when the license expires or the game is taken down?
It's not the perfect solution but Sony could easily implement it. Whether they want to or not is another thing.









