Dr. Mario also comes from a successful mainstream Mario series.
Heck, he even has his own franchise.
Indeed. Though it seems that Sakurai and Friends saw Galaxy as the more desirable series to represent in SSB4 (that is, supposing we won't get more than the present five Mario characters).
So then why aren't both in?
I'm not saying replacement, but there had to be a reason.
Other than replacement, I figure that it could be lack of time, that TL was always considered higher priority than YL, that Sakurai thought Wind Waker deserved to be represented in some manner.
Sure, but then you say:
But, according to your logic.
The Forbidden Seven is low priority. This includes the character you mention.
If anything, they'd have the same chance...
So the Seven had equal priority across the board (whether big or small)?
I would imagine that there'd have been a certain priority in the list - which is to say, if they had more time, they would have, for instance, picked Dixie to bring in first, then Toon Zelda/Sheik/Tetra, then Mewtwo, then the rest until they ran out of time and/or decided they had reached a sufficient amount of characters in the roster. It doesn't seem efficient to work on all seven characters at once, given the limits of time and development; they would have picked on the ones that were most viable, and include the rest if time allowed.
I'd see the priority as being Newcomers>Mewtwo (non-clone Veteran)>Melee Clone Vets (Roy, Doc, etc.). But I suppose we'll never know what they thought of the Seven.
I do think that of them all, Mewtwo's return in SSB4 is the most probable. But it's not a given.
You make a decent case for Doc, don't get me wrong. I think we can both agree that if he does make it in, it would be a (welcome) surprise, given everything going on (all other characters being worked on, etc.).
If Doc were to make it in, I'd hope that he would be further de-cloned (maybe have Pills with different effects, tie-in the DM Puzzle mechanics into his gameplay, etc.).
But, it does show a possibility...
We shouldn't be conflating possibility with probability.
All characters are possible, but some are (sometimes much) more probable than others. Not to say that Doc has zero chances, of course. At this point, it seems less likely that he'd get in as a Mario representative; if he is to make the cut, I'm leaning towards him representing the Doctor Mario series (as you also seem to hold).
If Rosalina, Wii Fit Trainer, and Toon Link (among others) got in.
He could be a decent "oddball" choice. Which Sakurai loves.
I don't think he would be all too oddball, especially since he
has appeared in a past Smash game.
I also wouldn't count Rosalina and Toon Link as oddball/left field choices either, given the success of Galaxy for the former, and the possibility of a no-Brawl-cuts approach for the latter.
As much as I enjoyed Mario Sunshine, I do also miss the raging Tornado.
Anyway, I think we're in agreement when it comes to Doc; he's improbable, but not impossible.