for cozy glow, id put the cutie mark crusaders in charge of helping her since they already knew her beforehand — including doing filly scouts stuff, which cozy glow probably hates. she would also become a teachers assistant to cheerilee, but that wouldnt be that prominent. i also saw some people say that diamond tiara would be a great help to redeem cozy, and im inclined to agree; i didnt show it in the pic, but i can imagine them bonding and improving as ponies together down the line.
chrysalis was the most difficult of the three because shes honestly the least redeemable — if everythings to be believed shes pretty much made to be evil. so i agonized a lot with her. ultimately i landed on her working as a royal guard under the strict supervision of all the princesses (when applicable) and shining armor, alongside pretty much the entire rest of the royal guard. and just to be safe… she'd be kept away from the changedlings unless the need arises.
as for tirek… well i guess this is obvious because of course id put her here somewhere, but i think letting fluttershy take care of his redemption would be a good choice, especially because she also redeemed discord, so shes kind of an expert in dealing with huge super powerful creature men. lol. also put him to work with others — maybe in constructions and such? — because this man needs the power of teamwork in his damn life (i would also like to cram scorpan somewhere into this, so yes, thered definetely be some family drama.)
obviously these three are still somewhat threats because i imagine twilight finally learns to not just give full trust to everyone all the time, so while cozy glow is already kind of nullified, chrysalis and tirek have to wear rings around their horns that nullifies their magic, ALL of it. even the most basic of magic; its probably a bit cruel to some, but its a situation in which youre better safe than sorry, pfft.
hmm… i think thats all i have to say for now. i just felt like putting this idea of mine out into the world and seeing what others think. i would like to do more with it once i get more time as well, but who knows if ill have the motivation for it.
(also, i really need to learn how to draw tirek better. i dont think id be having so much trouble because im good at drawing humanoids, but im trying to also mix a bit of animal in his face and i dont think its working :P guess ill have to study more to get it right.)