I absolutely believe they had a rough outline for the main plot, and that is probably more or less the same plan as it always was. You will not convince me that there wasn't a *huge* shift to focus almost exclusively on Nel and Nel-like content to chase the money once it became obvious that's what their paying base was most interested in.
It's blatant in the fact that the actual plot has been left to mostly flounder for years and you have these huge unimportant tangents like the ghost ship. Celica is not a character. Evie is not a character. Galiene is not a character. Faylen is not a character. None of the guild members are characters. The only characters are Nel, the other ghosts, Violet, and Glace. And besides Nel, these are all characters that so far have no impact on the actual plot. Glace was weaved into the backstory after her introduction, but I don't believe that was some thought out plan, just something that was thrown in after the concept of Glace came to be.
The game has literally just become, "Watch NPCs play the game instead of you." to satisfy this specific niche and that is blatantly not what it originally was going to be. And for the record, I say this as someone that primarily got into the game *because* of the possession stuff. But at this point I can't even enjoy it, because it's all just samey, boring, railroaded "Watch another character have sex with Evie" simulator. Because that's the only reason Evie *even* exists at this point, to be the token girlfriend character for other characters to cuck Celica with.