Ilina's existence is canon...
Selenic Shadow was just to make sure Cibryll's skills did not rust (I worked on the majority of it, but had her do things as well)...
Though now, both our skills are rusting away...
Shinica would be playable in Selenic Shadow, but since we made it all up as we went along, it is hard to say for certain...
The LSM trilogy have their own protagonists already...
Original Ilina, original Ilina... how original are you to be playable...?
(The best she currently has is being cosplayed by Kyaro in Apocalyptic Shadow... and the Umbrageous Light version of Ilina...)