New to v1.1, my buddy defnotreal has randomly added a custom character loader to Super Freaks 1 Ultimate Edition. Thanks a bunch def!
Def has also kindly provided a custom character template. It's disabled by default, but if you remove the ! in front of the name (or any characters' name) then the game will load the character, like so:

!example - WILL NOT LOAD
example - WILL LOAD

Inside the example folder are more instructions on how to create a custom character. More characters can be downloaded here: https://gamebanana.com/games/19289
Happy modding!