Hear me out. Shadow helping his brother come to the good side is great. But I recently had an idea where Sonic meets Eclipse and offers to go with him to talk to Shadow and explain HIS side. Cause Sonic is that kind of guy and he can tell the brothers don't REALLY wanna hurt each other. But he can also tell no one is trying to hear out Eclipse either.
Eclipse: why do you wanna talk to me???
Sonic: cause I think your voice deserves to be heard too
To this day, one of the biggest crimes committed by Archie's run getting canceled is that Eclipse never got to interact with any characters outside of the universe comics, ESPECIALLY Sonic.
Shadow eventually turning Eclipse to the good side is always a fun development, but I 100% think Sonic is a better and more realistic option for that arc. There's a LOT of possibilities for that development.
Where Eclipse and Shadow left off in Archie was pretty bad, Shadow was extremely paranoid about Eclipse being around to the point he had this imaginary Eclipse haunting him in his head (and yes I know the comic tries to be like "oh am I the real Eclipse or a figment of your imagination" but then immediately cuts to Eclipse running back to the dark arms to take care of them so I doubt its suppose to be the real Eclipse in Shadow's head) so for him to eventually WANT to bring Eclipse to the good side would take a while.
Sonic would be a lot more receptive to Eclipse changing sides. That's not to say he would help him right away, if he saw Eclipse as a threat he wouldn't hesitate to fight him, but the second he caught wind of how Eclipse really feels about Shadow or if he found out about the dark arms, Sonic would change his approach pretty quickly.
Sonic is easily the best person to change Eclipse's perspective on things. Sonic's skill in battle could leave an impression on him, it did with Shadow during/after the final boss in SA2, and maybe have Eclipse consider other species aren't as inferior as he thought. Sonic's love of freedom and nature could help Eclipse come to appreciate their planet more. Sonic would eventually find/interact with the dark arms and they'd probably take a liking to him right away while Sonic might resonate with the fact they're part wisp. Seeing the dark arms and Sonic interact would ultimately sway him into thinking "Okay, maybe I should hear this guy out." Then cue Sonic getting to work on the two brothers figuring things out.
WOOOOO a long post for me but I cannot end without mentioning this. If you're looking for a great story that includes Sonic and Eclipse interactions (or even the rare Sonic x Eclipse) I HIGHLY recommend Tides of Chaos by LightningHikaru on AO3. It's a Sonadow fic, but even if you don't ship it, I would give it a shot anyways because of how amazing the story, worldbuilding, and characters are in this story. This is one of the BEST pieces of writing I've seen for Eclipse EVER and I don't think a lot of Eclipse fans have read it because (well besides if they don't ship sonadow) Eclipse isn't in the tags, despite playing a MAJOR role in the story.
If you just want a taste of some Sonic x Eclipse content (because the fic pretty heavily implies Eclipse has a one sided crush on Sonic) I would recommend reading Chapter 34: Midnight Nightcap.
If you're disinterested in a Sonadow story but want to enjoy what an amazing story Eclipse has in it, His story kicks off in Chapter 21: Long Time No See.
Again, always want to thank ANYONE for sending me an ask, I just adore talking all things Sonic.