I think the closest person here to doing something like that was 5way...
Hey, I've just changed my name
(surprisingly enough there's an option that let me do it). I did the same on Twitch years ago since people was getting confused by "five-way" instead of "Sway" -I'll change my avatar later so people can get familiar with the change-
Back to topic; I remember replacing Gerogero's censored blue blood by the original red texture so I used a great tool called
Tim2View.
Choose "File" then "Scan file" and pick the desired comxxx.dat, the texture(s) will show up and you can extract them as *.png (or *tim) files. The tool also offers clut details and more details about the texture.
Once editing is done you can import the texture either as *.tim or directly *.png which is quite useful.
Good luck Sega!