A random discovery from messing around. There are two pairs of files, one makes the model invisible and the other one makes his SFX disappear (ki charge, Masenko, Kamehameha, Potential Unleashed, etc). You can use all the files simultaneously.
A bug I found is that Gohan's intro will never have the ki eruption so, after his dialogue, the cinematic must be manually skipped (unless you like looking at the background).

Extract and put the files in "~mods"