Warning: the following is a really long post, my apologies if you find it too long to spend reading.
As it's the topic that is most focused upon whenever Super Smash Bros is brought up in a thread, I guess I'll start with my thoughts on the characters.
I like the idea that the roster won't be expanding too much. I've seen many, many suggestions on threads that this next Super Smash Bros should have over 50 characters, which always seemed a little ridiculous to me. From what has previously said, it seems they will instead be keeping it closer to 35, more than likely replacing a couple of characters, so my bet is the roster consisting of about 40 characters. I'm not a fan of replacing characters in games but they will probably do so with this game, and so the ones I would replace/remove, would probably be the following.
* Toon Link - We already have a Link in the game, and they've never taken the potential opportunity before to make these younger Link's unique to Link. I personally think they should either stick with just the Triforce Trio, or add in a different Legend of Zelda character.
I know I will probably get quite a bit of hate for this, but as far as a new Legend of Zelda character addition goes, I think the character most deserving of this is... Tingle. Think about it, he has multiple appearances, multiple playable appearances at that even with his own spin off games where he is the main protagonist, and can have a unique move set based around his unique games. Furthermore, previous polls and discussions have shown an interest in having Balloon Fighter as a playable character, but why bother with Balloon Fighter (unless you are going to suggest Balloon Kid's Alice, because this game could always do with more female characters) when you could have Tingle, a character whose been the star of a Balloon Fight game and has much more potential for a possible move set.
Other than Tingle, the only other Zelda series character noteworthy enough to deserve a spot is Vaati, a choice I would be okay with as this adds more villains to the roster. I personally am tired of seeing one-time characters such as Midna and Ghirahim being so highly suggested, ignoring Zelda characters more deserving of the spot such as (despite how much people don't like the guy) Tingle or Vaati.
* Falco - Falco replaced by staff wielding Krystal. It adds a new female character, a highly wanted character by many fans, and has a Star Fox character with a unique move set. The only reason I suggest Falco to be replaced instead of Wolf is because Wolf fills in a Villain quota, and has a more unique move set than Falco's.
* Pokémon Trainer - One of the reasons Mewtwo was removed from Brawl was because the creators felt that they had too many 1st generation Pokémon in the game. This has always confused me then as to why they included a Red/Blue Pokémon Trainer with the three first generation starters. So my idea for Pokémon Trainer is to keep the playstyle, but replace the 1st generation Trainer and his Pokémon of Squirtle, Ivysaur, and Charizard.
Now, before the 6th generation was announced, my thoughts concerning Pokémon Trainer were to have him replace with a 5th generation Trainer, though preferably an actual Pokémon character, rather than your personality void protagonist. Case in point I thought N would be a decent suggestion, as it would make sense if his squad consisted of, well, just about any 5th gen Pokémon, though they probably would gone with the starters (which is a shame, as 5th gen was the only time I disliked the starters). It would also make sense if for his Final Smash he just sent out Reshiram of Zeckrom against everyone, possibly having a difference between which one depending on whether you are playing the Wii U or 3DS version.
With the announcement of a 6th generation though, I imagine they will want to include a 6th generation representative so I can see it making sense to have the 6th generation trainer with a squad of the 6th gen Pokémon. My only wish in that case is that they allow you to play as both the male and female trainer, it wouldn't affect gameplay after all, and with a nameless protagonist who sits in the background for the fights, would be a plausible option.
* Lucas - I've no idea why they included Lucas, when previously they had said they wanted the characters to appeal to all their audiences. It's funny then that they included the Japan only Lucas, and at that, he doesn't even appear to play like he does in the games. I will admit, I have not played Mother 3, but from the information I've looked up Lucas seems to be the healer of your party, with a general lack of offensive moves.
As for Mother replacements for Lucas... I don't think there should be one. While I've heard it is a great series, the Mother series still consists of only three games, and as far as I'm aware, only Earthbound made it out of Japan. Frankly, I feel Mother should be okay with just one representative.
Now, to be clear, what I have said is only my opinion. I feel, if they replace or remove characters, then these are the ones they should replace/remove to allow more deserving or better suited characters to appear. Moving on then, when it concerns characters I would like to see appear I know there are some which I'd like to see but probably won't or deserve it like Bandana Dee or Ashley, so I won't go through the trouble of suggesting them. I also know the roster isn't going to have all that many new inclusions, despite how I feel that there are some characters that really do deserve a spot on the roster by now such as Little Mac and Starfy. Instead I'll just state the two characters that I most want to see appear, and why they deserve to appear on the roster.
* Ridley (Metroid) - Size should not be an issue. In Super Smash Bros Brawl they were able to increase Olimar's size, so why not shrink down Ridley. Heck, you could even have an explanation for that in the story mode, if they wanted to. Furthermore, Bowser's size changes constantly in his games so really, I do not see why size should be an issue.
As for why he should be included, well he?s the arch-nemesis of Samus, the second most recurring character in the Metroid series, and Metroid could really do with another representative. He also fills in a villain spot, and if this goes along with my removal of the original Pokémon Trainer, and thus the removal of Charizard, his A attacks could be done in a manner similar to Charizard?s (I imagine there would be some differences in regards to the special moves). I also really like the character.
* Lip (Panel de Pon/Puzzle League) - This probably seems rather hypocritical considering my reasoning for the removal of Lucas was based on Japan exclusivity, but Lip covers areas that Lucas does not. Lip was the main protagonist of the debut game for the Puzzle League series, she?s a retro character that is often brought up (such as her appearance in Captain Rainbow), would be a decent representative for the puzzle genre (even more so now that Dr Mario is not in the game), is a female character and at that is a female character that is the main protagonist of her game. Again, I also really like the character and I believe that there could be some interesting and intriguing move sets and play styles created for this character.
Now then, I believe this post is getting a little too long so I?ll stop here and return to comment on features later.