Well, there's probably more underneath the hood, but for those of us who are looking at the writing credits for each album, the tracks are attributed to "A Ghoul Writer" Who is this writer? Is it just Tobias or are there more names underneath the umbrella? Interesting to me at least is that on Meliora, the credits are A Ghoul Writer and Indio Marcato for some tracks. Indio appears to be a pseudonym for someone as there is absolutely nothing on the internet about this person and no other works. So who is that? So I'm guessing they'll get no writing royalties. The best I could see is them getting is some merch/tour royalties.
The keyboardist has been the same since late Opus Eponymous through Meliora. When Ghost started touring, the keyboardist was just piped in through the speakers, the guy onstage was just there for show. Then they got the keyboard player, who I think is Mauro Rubino, some old keyboard player that used to play in different prog bands in Sweden. But yeah, you're right it was Tobias, Omega, and Alpha as the only constants throughout the seven year period until now. It will be interesting to see how it all plays out