If nothing else, you'll need to rework the verifier. The time complexity of verification is super-linear right now. Awhile back I proposed a linear time algorithm that was a bit stricter, but it didn't get implemented.
Also, from memory, there aren't real stack frames right now. (This is a limitation of the implementation and the verifier, not a fundamental issue.)
I was reading about eBPF and how it's instruction set is easily JITable across several architectures. I was wondering if it would be good as a VM for retro games. Something like Pico-8 [1], but where one could write games in this restricted C or eBPF-ASM.
As I understand it the VM calls specific functions with limits of calling convention (10 64-bit registers shared between arguments, returns etc.). VM can also expose helper functions. It seems quite capable for such a purpose.
Where could I find more materials to explore this side of eBPF? I found a user space eBPF VM [2] - probably a good start.
EDIT: In case anyone is wondering: Why? For fun!
[1] http://www.lexaloffle.com/pico-8.php
[2] https://github.com/rlane/ubpf