I made Musha Nu Gundam using the new BB Senshi Nu Gundam as a base. I think I was imitating something from a hobby magazine or something back then. I made it by recalling photos I'd seen and looking at the original BB Senshi product, so there are quite a few parts where I just filled in the blanks, but I was thinking it would be fine as long as it looked cool...
I roughly made the shape with a 3D printer and filled in the gaps with putty, so I remember just going with the flow and the back being messy.
My cheap 3D printer has died, so I may not be able to make the same thing again (TOT)

Legend BB style Musha Jin'u Gundam | やきにくふらいでー's Gunpla works