1. The documentation needs to include detailed help on the json files for us free users, especially on what color-map does and how does music.json work. Oh, and on DrawModes.
2. I'd like some features of Chip-8, like xoring (maybe anding and oring too) sprites on top of each other and 16 key keyboard support (for future mobile builds, check out Android app ChipChip).
3. Attribute clash would also be nice. This is what any other retro game engine wouldn't want to provide.
4. I don't know if PV8 already has it, but ZX Spectrum has a good simple beeper.
5. One of the reasons why PV8 is not widesperad further is because downloading it requires registering for the Club, which might deter many people.
Nobody announces their PV8 games. It's like I'm the only one. The community is surely lacking.
Anything I'll think about later would be in a different comment.
And most of all, thank you for being so passionate about retro platforms.