It wouldn't really be polyamory, exactly, since, in theory, Scott/Jean/Emma/Logan (and others) wouldn't really be together, it would just be separate couples. One couple might get exhausted, but other pairings involving one of the characters might not.
Exactly.
For example, one thing I often complaint is the retcons to Emma's origins, for example (we got at it often in her Appreciaton Thread)- she, under Claremont (in the 80's), and Morrison (early 00's, there being a middle aged man already) established Emma as someone that was Shaw's not only equal, but better, who made him think she loved him, but screwed him over, and really didn't care about anyone but her students and a handful of people (which is why she falling in love with Scott shocked her, because she didn't even think that was possible but in romance stories).
Then Fraction comes and establishes her as Shaw's stripper turned abused girlfriend caught in the dick measuring contest between alpha male one (SS) and alpha male two (Namor), and who also falls for Namor after knowing her, for, what, one week, and is willing to abandon everything she built to be with him, only for her mind to be erased by Selene (the fact that Namor does not ask help for his friend Xavier of the Illuminati is left unexplained, of course, or why Sage didn't inform Chuck herself). He's basically regressed her origin from shrewd businesswoman to stripper with a heart of gold victim of an evil alpha male who could only be saved by another, yet he almost certainly fancies himself as a progressive, as well as the editors that approved that story.
Later on, other "progressive" writers and editors continued on the abused girlfriend story rather than just retcon it (easy enough, with her being a telepath with a long story of deceiving people).
The difference, being of course, Claremont and Morrison are truly progressive writers, the others...not so much.
Thunderbird was killed and Sunfire left in a plot by Len Wein (Claremont just did the script).