There can never be a winner in an argument like this, because each side can always pull out proof that proves their side (or refer to it).
And before I dive in, let me say that the two figures that pulled me in to MOTU Classics were the Goddess and Wun-Dar, so I understand obscurity.
TG has a point in that inside the pool of MOTU characters - the "this is every character ever from every continuity and line list" - Illumina has a low level of recognition outside of .org. How could she be known? She was featured very little for reasons already stated in this thread.
Inside of .org, I would say that EVERYONE knows about her now.
My personal research - i.e. me talking to people I meet in person or see my collection - would say that in the category "I only collected He-Man between 1982 and 1987", no one knows who He-Ro, Tytus, Carnivus, etc are.
And one guy was confused by Scare-Glow, saying that not even the original line is known to all toy collectors.
Instead of the ToyGuru "ask a question that surely will piss off at least 50% of the people you ask" method, I have a more simple strategy. I think that Illumina is a demanded figure - to a small audience of MOTU buyers, primarily situated around .org but slowly expanding. She'd also be a fine choice to those of us who bought a sub and are fine with anything that Mattel puts into it (I have no stats on this because there are generally no complaints in this sub-group of fandom).
However, I think that argument could also be made for many other MOTU characters. I lurk at the .org and see threads devoted to Josh from POP, Songster, yellow Tug-of-War guy, pilots from box art, random NA characters, Filmation characters, "fix He-Man's hands so he can do one more pose"...in my view, you have your " absolute top demand" figures: Ram Man, Mekaneck, Two-Bad, Spikor, Jitsu, Mantenna, Modulok, Horde Trooper.
Then there is a "we're pretty sure this would sell out quick" - Mosquitor, many POP figures, etc.
After that is a vast wasteland of pockets of support, with varying levels of want and loudness.
I know I have read a thread about "toy design Star Sisters", when the versions coming have yet to be released. Or for a true 200X Evil Lyn - even some for a 200X He-Man.
I myself would be one of the posters in the "Make all the NA figures!" thread, but realistically, I know that many people do not want them, or at the least, are not fired up until they see the Horsemen versions.
And that is the problem with Illumina that Scott failed (and continues to fail) to illustrate. He'll never win with scientific proof that the active posters on .org are a certain amount of people buying MOTUC. Or that Mattel has a crack research team that told them that RockEm SockEm Robots would be a hit back in the year 2000 and is smarter than .org. Or by saying "do you want Ram Man or Illumina?"
The truth is not that Illumina is less desired than so many other characters - but that she is desired just as much as many of them.
AND that we all want our favorites - but that no amount of fan pages and such are going to get Quakke moved up in the lineup. Oh wait, that is my most wanted Classics figure.
Anyway, I hope to see Illumina in the line someday. And Quakke.