My "headcanon I am married to" is called "The Masked Empire" - you know, the novel from Bioware (I guess you do not know, oh, well). In that book Gaspard is planning (and even executing" different plans about murdering Celene. But I suspect your dear husband (aka your headcanon) would never let you read or understand that book. Too bad.
Oh I'm sorry, my version of TME took place before the ball at the Winter Palace, so I missed the part where we were told about what happened after the assassination! As I said in a previous post, yes Gaspard was indeed planning to somehow have Celene removed from the throne, however method worked best. That would indeed include murder (he'd also go for marriage, or her dying in battle). He *knows* very well how to play the Game. That *still* doesn't mean that if he'd been caught in the act, which is how the scene at the ball would've played out without the Inquisition, that everyone would just go "oh well guess you're it then Gaspard, nothing we can do about it!".
And yes, it is indeed my headcanon, because there is nothing stated explicit in-game about why Orlaise was in turmoil after Celene's death. Your point is...? I mean, when you aren't too busy trying to take cheap shots at people instead of discussing?