I think the best thing is to not assume that spirits deconfirm characters period. That way they all have a shot. Also Sakurai does have a way around that when it comes to Shantae. We ALL know how he can get around that "rule" or "argument".
Yeah, my philosophy is assume what makes the most sense, but already allow for the possibility to be surprised.
As long as it is physically possible for a character to be codes into the game, then it's "possible" for for them to be added. Doesn't mean likely, just means that any "rules" fans imagine existing don't really mean anything.
Sonic and Snake showed characters didn't have to be owned by Nintendo. Cloud and Joker show they don't have to have a presence on Nintendo consoles.
So if that being said, there had been no word on Spirits for or against and everyone is just assuming what their existence could mean for characters.
Personally I feel there are too many in demand characters as spirits that off they were deconfirmed, Nintendo wouldn't have many characters to pick from. It would be needlessly limiting yourself. I mean, basically the only 1st party characters they could use are only ones made after Ultimate at this point cause nearly all the notable ones are already spirits. And I really can't think of 5 worthwhile 3rd party characters (the I have biases against a lot of 3rd party front runners)