While for me I can take or leave the Illumina character (she is cool looking and I wouldn't mind having her in the line since we are getting obscure characters anyway, but at the same time if she doesn't get made I won't lose sleep over it), I will say that it almost seems like Mattel is going out of their way to make a series of catch-22 excuses that just disqualifies Illumina no matter what.
I can understand that semantically she wouldn't fit in with the 30th anniversary sub line. That's fine. But none the less, Mattel doesn't have a problem with taking a chance on something like a 30th anniversary sub line made up mostly of original characters that fans have never heard of before (save for Photog), but somehow the idea of including Illumina somewhere, some way, some how in the MOTUC line is something that they just aren't willing to gamble on.
Heck, what about characters like Vikor or Gygor? I don't really remember there being that huge of a demand from the fan community for either of them prior to them being announced in the line (especially Gygor, and he is an oversized Beast, as is the upcoming Griffin, which didn't seem to have a huge demand either).
And even a variant like the blonde bikini Teela. That did certainly have a strong demand and following, but I don't know if it was much more than "50 very vocal fans". And even the upcoming Sisterhood-Of-The-Traveling-Pants Convention Sorceress figure is an obscure variant based on a single mini-comic. Sure the latter 2 that I listed are obscure variants of well known characters, but the fundamental point remains the same.
There has been a lot of chances taken with a lot of obscure items in this line, but somehow Illumina is stuck in this weird catch-22 limbo where she's either too obscure or (in the case of the 30th anniversary figures that are original and completely previously unknown to the fandom) not obscure enough to get produced somewhere in the mix.