speaking of iconic, I once saw an interview with sakurai about how he chooses characters to get into smash bros, and I think it sheds some light as to how realistic of a chance every character has by default. I can't find the source and it was a while ago so take this with a grain of salt.
1. Is the character iconic or has had a significant impact on the videogame scene? cultural or otherwise? If yes, it's more likely to be added.
2. Does the character have something only they can do? A move or otherwise? If yes, it's more likely to be added.
3. are they a recurring character?(implying the series has to have more than 1 game) If yes, also more likely to be added.
4. Are the creators of said characters willing to be in smash? Obviously, if no, then it will won't happen.
5. Are there still lots of fans of the series? If yes, as always, it's more likely.
6. Main characters are preferred over side characters.
There are two more I thought was in the list, but with recent additions I think he may have backtracked on them.
possibly backtracked 1: How many others from the same series is in the game? The more there are, the less likely the new character is from being added.
(This rule was probably either eliminated entirely from his consideration or he doesn't apply it to fire emblem characters, as always, the rules aren't set in stone anyway)
possibly backtracked 2: does it make sense for the character to fight in smash?
the villager makes little sense, I think he was cut out of brawl for this reason. And later added back to newer smash games
and pacman, althrough he did have a game where he brawled with other people.
There were a few more but I flat out can not remember the rest. These were the ones that stuck out to me.
I believe simon belmont hit more of these than ashley does. And serves as a useful guide for predicting future smash characters.
When I wrote them down, it really seems like common sense, doesn't it?