Skyrim is full of surprises... on nexus is a new mod https://www.nexusmods.com/skyrim/mods/93543?tab=description ... with some clicks you are able to create a new npc (even clone yourself) and the new npc can be recruited as a full follower...

Here my player.char is a custom race ( winged twilight ) .. the follower is a nord-race-female, created from the preset of my playerchar... (had to change the playerrace to nordrace, temporary to create the new npc)... after creating changed back to the custom race... and now a "twin", slightly different looking is following my adventures...