You don't have to do it this way, but it looks like the code to be interpreted is normally compiled to bytecode stored in a constant in a C header. So it's all in flash anyway, and you'd update the flash the same way as changing C code.

If you're going to do that, why not generate C and skip the interpreter? Is it because bytecode is more compact than native code?

I guess there would still need to be a runtime to handle array memory garbage collection.