Did anyone ever get a chance to talk with Terry Kavanagh about who he intended Masque to really be?
As soon as I saw your post, I asked Kavanagh about this, on his Facebook page. After several days, my message was not answered. Checking today, I saw that the message was viewed, so I highly doubt that he will ever respond.
Which doesn't surprise me. Back in the 90s, he was happy to claim the paternity of The Crossing storyline, in the now defunct Wizard magazine, only to disown it about 2 years ago, when asked about it in a post made on Len Kaminski's Facebok page. As he did not answer who then, came up with it, I doubt that he has any interest in contributing to clarify this matter.
Apparently, this will only be clarified, if someone who worked at Marvel at the time, decided to tell behind the scenes stories about what happened.