While I would never consider this approach advisable in any language that doesn't build in support for this sort of thing from the start, the thinner the runtime, the less dangerous it is. Go's runtime is fairly thick, and also, concurrent. The odds of something blowing up are rather too high for me to even dream of putting something like this into production in Go. In C++ it may merely be somewhat crazy rather than completely crazy.

(I suppose Rust is arguably an exception to this; thin runtime, but there's a lot of things the replaced function could do that would still blow Rust up if the rest of the code isn't compiled and correctly optimized to account for whatever the new code does.)

You could already do that today, via OS IPC mechanisms, at the expense of higher systems resources, with each plugin being its own process.