But to be honest, I wonder what is the smallest interpretable and practical Turing Complete VM? I would argue that implementing a brainfuck that we lower Python interpreter to, or even say like an interpreter untyped lambda calculus or SKI combinator would be very useful, especially for the hardware bootstrapping.
I'm talking about things like SectorLisp https://justine.lol/sectorlisp/
I think we would need to balance practicability and code size since they tend to be mutually exclusive. Generally speaking, code size is not an important metric to make useful code, and usefulness is usually not the main point of code golf exercises such as this one.
The exception to this is obviously embedded systems with very low amounts of resources where C and assembly are practically unrivaled.