First, thanks to all mamedevs for making 2020 such an amazing year with so many great new features and additions.
Here's a top 10 for the new year, in order of "cool factor", borrowing somewhat from previous years:
1. Support for cross-platform (SDL2) rumble effects for systems like the PSX (dualshock), N64 and PokeMini vs. the basic output handler support that currently exists. Would be so great to see even if it seems like such a moonshot now.
2. Model 2 accuracy improvements
3. Macintosh Plus/512 speed fixes to resolve this issue
4. More accurate Cave CV1000B timing
5. BGFX vector bloom
6. Framework for future improvements to BGFX presets (examples include optional auto-assignment of "arcade crt" to arcade systems, "green screen crt" to apple //c and "green screen lcd" to original gameboy)
7. Improvements to high-profile console drivers such as nes (more accurate ppu), pce-cd, atari 5200 and n64 (speed optimizations)
8. Broadened discrete circuitry support to include more DICE games and others such as Monaco G.P.
9. Support for Mattel D&D, an excellent LCD handheld with infinite replayability
10. Proper support for Primal Rage II to put an end to other hacky efforts in existence
As with previous year wish lists, most of these aren't entirely practical and I'm certainly not expecting anything here anyway, though it's fun to imagine.