I can just imagine some space base with mycelium sprouting out from between the modular wall panels. I think this is a bit unrealistic since mycelium is pretty much always alive, like the whole thing is a seed. So unless you kill it and make it leave behind a husk it's just going to cause trouble.

I'm actually just making a biased opinion/guess here, so I'm certain I'm only half correct, but yea I don't see this being a true solution when other expanding/growing insulation also works