Using a spare Saiyan Raised on Earth Goku body, I made another Future Gohan but this time with one arm. Some fodder heads were shaved down, resculpted, and painted to match Future Gohan. The middle stripe on the front and back of the boots were sculpted along with the long shirt sleeves. The shirt sleeve of the missing arm is sculpted so that it is empty and folded. Lastly, Gohan's kanji 'han' was painted on the back.
*** 7/1/20 edit ***
I redid the base form head, sanding it down and fixing the bangs & spikes. The SS head was slightly modified as well.
I took the Jakks Bojack head and put it on a Figure Rise SSGSS Gogeta. The sash and lower arms were sculpted and his scar was carved onto the body with a knife. The whole figure was then repainted to match the movie.