Interesting, I tried it on a small game I've made and it fixed all missing function issues except tostr. There were no assets, which contained level design so the game is not playable, but it seems promising (even with the game assets I would still need to replace the missing sprite flag feature in TIC-80 by manually calling fset at the beginning of the game... not designer-friendly, but ok).
For remaining functions like tostr, you can get some inspiration from pico-love, since they also adapt PICO-8 functions to native Lua: api.lua
I use myself a simplified version for my unit tests that run directly in Lua (pico8api.lua). Since I don't test rendering, most render/audio methods are empty, though.