Gengar chances: 0.3%
For all practical purposes most Pokémon have 0% chance of becoming playable in Smash; only a limited number of them would claim they're at least remotely possible. Considering its popularity and symbolism as the first Ghost Pokémon, Gengar may be one of them. However, I doubt it would be much of a high priority, since a gen 7 Pokémon would be more prioritized. Maybe if Sakurai has the time to put more Pokémon characters and Gengar beats the competition in that, then it might have a chance. Not an easily dismissable impossibility like at least 95% of existing Pokémon, but not likely at all either.
Gengar want: 27%
I don't feel the need of having Gengar playable, but it's a fairly iconic Pokémon, so I guess it'd make some sense at least.
Rate Their Chances, joke character special bonus edition, day 3: double zeroes (yet again)
Okay, let's have a fun experiment with maths. Suppose we give this combination a 1% chance rating. For the sake of consistency we might also want to give a 1% to any combination of second generation characters of FE Awakening (13 according to
FE Wiki, minus Lucina who's already in Smash as her own character, or 12). This means there are 66 possible different combinations. So let's multiply 0.99 by itself 66 times, and we get a result of 0.5151 followed by a lot of insignificant numbers, or about 51.51% of getting none of them. That means about 48.49% chance of getting at least one of those combinations, or almost a coin flip. Imagine you flip a coin, you get the results you guessed first, that means a combinations of second generation characters from FE Awakeing becomes a playable character. Sounds unreasonable, right? If you change 1% to 0.01%, I'll skip the calculations and just tell you that by the same process we get a chance score of getting at least one of these characters of about 0.66%. That's roughly the probability of getting Mew out of a Poké Ball in the original Super Smash Bros. Very unlikely, but not impossible at all. Imagine you're playing the first Super Smash Bros. and you bet that if Mew appears from it, a combination of two second generation characters from FE Awakening becomes its own character in Smash. Do you think getting any such combination is anywhere near as likely as getting Mew from a Poké Ball in the original Super Smash Bros., or any Smash game for that matter where the chances of getting Mew got increasingly smaller due to being equal to the number of different Pokémon existing at the time of each Smash game? If you have more faith in getting Mew from a Poké Ball in any Smash game than getting any combination of two second generation characters from FE Awakening as its own newcomer, then you have no justification giving the Yarne & Owain tag team anything higher than a flat zero, unless you can somehow make the argument for this combination in particular being more likely than others, say, for example, Cynthia and Gerome. The problem is that in my mind, considering my knowledge of FE Awakening, you would need to do something extraordinary I'm personally incapable of imagining to convince me: while I believe Owain is fairly popular, being for example the only FE Awakening second generation character to be playable in FE Warriors besides Lucina herself (so maybe we could limit ourselves with combinations only involving Owain, giving us a probability of 0.11% of getting at least one, or about 25% less likely than getting Mew out of a Poké Ball in Smash 4 which put into perspective I believe is still too high), I have no reason to believe that Yarne particularly stands out. In addition they have basically nothing to do with each other, not even support dialogues in FE Awakening. So if you care about mathematics, please give this character idea a flat zero.
Yeah but anything is theorically possible, claiming that they're absolutely impossible is arrogant!
It's completely true that you can't claim with absolute certainty anything about the reality that exists outside of your mind, not even that such reality exists on its own right regardless of the existence of your own mind: maybe it's just a dream after all, and it's also why in the philosophy of sciences you can at best only pretend that a theory about the natural world is very likely to be true rather than absolutely proven. But while there's no such thing as absolute certain, there's however such a thing as so unlikely it's for all practical purposes impossible. Remember the story I wrote for April fools day involving a god, people able to communicate with him, violations of solidly supported laws of physics and huge conspiracies? It's in theory not impossible that all those things are real, but it relies on so many grandiose ad hoc hypotheses that it can for all practical purposes be considered impossible. This character duo idea is the same: there's no reasonable reason to assume it's remotely possible without claiming grandiose ad hoc hypotheses. It's just an RTC joke and it's unlikely that such an idea would ever cross Sakurai's mind in the first place.
I have no reason to consider this idea remotely possible, I have no reason to think it's a good idea, and I have no reason to want it on a personal level. And it's not hilarious enough to make up for how random and nonsensical such a character addition would be.
Masked Link prediction: 6.48%
B.B. Bandit Trio prediction: well since Bubsy and Brash did get scores higher than a flat zero, and – ohgodwhy – even the Yarne & Owain Tag Team did, I have no faith in those getting no score higher than a flat zero, so I'll instead predict 0.84%
Nominating:
Playable newcomer: Cynthia and Gerome tag team x5
Concept: Battlefield form stages x5