I have the 1/35 Italeri MAS boat kit. I am definitely planning to do that. The deck is one piece and is held down to the hull by screws. Hiding them isn't too challenging.
The below deck is pretty spartan, crew room forward, pilot house well, engine room and fuel tanks.
The hardest part of it are those three big Isotta Fraschini 18 cylinder three bank monster engines. I can't find anything even close. Oh and there's a little Alfa four cylinder inline for puttering around. Otherwise not a hard project.