The Fugaku was never actually built, so you can make it out of whatever you want.
As to the propellers, brown
paint was a standard Imperial Japanese Navy color for metal props and the
supposed designation of G10N1 was an IJN desigantion, so therefore artists use IJN paint schemes.
Wooden props were in common use in high-performance aircraft by both the Allies and Axis during the war
and wooden propellers performed no more poorly than aluminum or steel propellers. Nor is a properly designed
wood structure automatically weaker than a metal structure.
Here's a page that may be of help:
http://www.enginehistory.org/propellers.shtmlAs to inherent structural weakness in Japanese bombers, ?, what
inherent weakness are you referring to?