I love, love, love Ben's videos, and this is an awesome project.
But to be as painfully pedantic as possible: can we please use the word 'monitor', here? Calling it a 'microkernel' really gives one the wrong initial impression.
Still, very neat. Now write a BASIC!
> Now write a BASIC!
No doubt an educational project. However, all the versions of Microsoft 6502 BASIC were collected and annotated by a Michael Steil in 2008.