And, I'm cherry picking
Maddy was a tabula raza before imbued with the life force that originally belonged to Jean...was sent to be returned to Jean after Dark Phoenix died, keyed to Jean's DNA...Jean in the cocoon rejected it due to the horrible memories of destruction attached to it...so it bounced around to Maddie instead.
One key aspect of Jean originally being uncomfortable with the idea of Rachel was not just that it was a daughter from an alternate timeline, but what that timeline entailed...DOFP, Sentinels, mass mutant death, etc...it made it feel like everything the X-Men/X-Factor were fighting for would be for naught.
But this was all resolved with Excalibur #71, the wedding, and Adventures of Cyclops and Phoenix...and everyone got the memo except Guggenheim
Maddie was always a cheap Jean replacement in the the Marvel universe and in ours, down to the genetics, absolutely nothing more
Her whole existence depends on Sinister/Claremont wanting to make a Jean/Scott baby and not having the real Jean avalible.
I feel like we're having an info disconnect. I'm talking about the souls of beings being identical, while talking about real life twins. There isn't evidence to suggest a soul exists in the real world. So saying that two identical twins in the real world have identical souls isn't something that can be proven.
Which was basically Claremont repeating what he and Simonson did in Inferno already.
I do like Madelyne as her own character, especially after reading Mutant X a few years ago and seeing her stand on her own, but the fact is that she never should have been brought back. That's what made things messy.
"We come into this world alone and we leave the same way. The time we spent in between - time spent alive, sharing, learning together... is all that makes life worth living." - Jean Grey
Yeah, IMO she was doomed to fail. CC made too many coincidences. Scott could have moved on with someone like Lee Forester...or designed Maddie differently...but the physical resemblance(atrong enough to sometimes produce a visceral reaction), the backstory, plane crash, sole survivor, having the plane crash the same day Jean/Phoenix "died"...was begging for some kind of convoluted retcon...and we got it