I have an idea to include them in a way that does not diminish the awesomeness of Shadow Jago, instead of them being actual shadows have them be just shadow in name only. By that I mean reuse the character model and change some stuff to make them new enough to be as unique to the originals as shadow jago is to jago visually. Some examples would be
Roxy Rave as Orchid’s Shadow
Eagle as Fulgore’s shadow since he is based on Eagle so I assume he would share some of Fulgores moves
Revived Eyedol (his split heads heal as 2 separate cyclops heads and his armor is body and armor are repaired) as Eyedols shadow
A Wolfman that has bats following him that works for Mira as a shadow sabrewulf
Now that they revealed shadow skins are coming this kind of idea would help if we ever do get more bonus characters like Omen and Shadow Jago