Well, my first suggestion for a PS1 Mini would be that it should come with a specific number of games, with the option to buy/ download more. The inability for me to expand the NES Mini's library beyond what it offered at launch is the main reason I didn't buy one. Anyway, my suggestion would be 20 games included in the box, at an $100 price point ($5 per game). I would want...
Resident Evil 1, 2, & 3.
Dino Crisis 1 & 2
Silent Hill 1
Final Fantasy 7, 8, 9, & Tactics
Metal Gear Solid
Crash Bandicoot 1, 2, 3, & Crash Team Racing
Spyro 1, 2, & 3
Castlevania Chronicles & Symphony of the Night
This would be a pretty great, diverse list of games, I think.