Thank you for the kind words :)
I would be against loosening the limitations in such way. If TIC is supposed to be a fantasy computer, I would rather have fantasy limitations. I think TIC is a strong contender to be a fantasy computer to pico8's fantasy console.
Most of the 80s computers and consoles had a limited palette. If not not limited to single color palette, then it would use like 8/16 colors out of 64 or something similar. Same goes for fonts. Very few systems had multiple system fonts, and if they did, they usually corresponded to a different graphic mode.
From my experience with pico8, I can say that those limitations spark creativity, and attract people to the system.
Also, clear cut limitations is what made pico8 stand out. There is a lot of small game engines out there, but they seldom gain a big following. If you try to do everything you will get lost in a sea of lookalikes.
Saying all that, there wouldn't be anything stopping programmers from including their own fonts for their programs by utilizing the sprite sheet and some code.