What are each of the turtles + Splinter + Aprils best case scenarios for when Donnie comes home? Would they want him to be the same? More open and communicative about his experiences with Draxum? What are they hoping to get back once Donnie is returned to them?
I think Leo is the only one who's really banking on Donnie being the same as he was. He knows logically that he won't be, and he still loves Donnie unconditionally, but it's a hard truth for him to swallow. Despite their butting heads, Leo and Donnie have always had pretty good reads on each other and it's just unthinkable that he doesn't know his twin inside and out anymore. If Donnie remembered who he was today (or, you know, whatever day it is in the fic) and went home, Leo would be be very supportive and understanding that he won't be the exact same Don he was before, he would internally struggle with it a lot, and would probably start getting frustrated with Donnie after awhile if he didn't acknowledge what he was feeling.
Raph I think isn't thinking too much about the emotional aspect. He also knows that Donnie will be different, but he's not pinning his hopes anywhere. He just wants Donnie home safe, and maybe not biting him. Like yeah, he doesn't want Donnie to be mentally or physically hurt, but he'll worry about that once he's home and with family and Draxum can no longer hurt him. He said that he'd accept any Donnie he got back. He just wants his brother to be safe.
Mikey, he's probably the only one actually acknowledging that Donnie's experiences have changed him in a way that cuddles and hugs can't heal and actively thinking of ways to ease the transition and help him in the days after. It's hard because he knows so little about what happened to Donnie and what he's thinking now, but he's trying. Ideally, he'd like to have Donnie come home by choice, either by having his memory jogged or by realizing for himself that something is wrong. (and yes, he would like Donnie to be very open with Dr. Feelings about everything that happened, but he also knows that this is Donnie and Donnie might respond better if they don't push him for details)
April is probably somewhere in between Leo and Mikey. She knows that Donnie is going to be messed up and she accepts that. She wants him back so they can get the healing process started. She keeps telling herself that she'll be happy as long as Donnie still likes JJ and performs spontaneous musical numbers with her. It just hurts. Her greatest fear is that Donnie will never remember her.
Splinter, oof. Splinter's actually going through a bit of his own arc right now. In all honesty, he's terrified by the idea of Donnie coming home. He wants Donnie back asap, obviously, but then he'll know for certain what all Draxum did to his baby boy. And Splinter is already five stories of pure homicidal rage pressed into a three-foot rat body. He's not sure whether to wish that Draxum's already dead when Donnie tells him everything or if it would be better to fantasize about everything Splinter's going to do to Draxum before he kills him while he listens to that. He just...wishes he could make the pain go away. There's too much in this world that dad snuggles can't make better.