There's still the issues of the controllers, which are the digital-only originals. Lots of things to overcome to make this thing more versatile for the platform.
It's not a *huge* issue IMHO. Save for very few exceptions like Ape Escape, DualShocks were optional for games even going into the end of the PS1's lifespan. All of the extra games Pixelboy listed were perfectly playable with the stock controller, IIRC.