Alright.. I guess I'll finally think about my top 10 (avoided posting in this thread because it's really hard for me to come up with my 10 most wanted characters..).
1. Knuckles
He's my favorite video game character along with Sonic, but even cooler. He fits well into a fighting game and Smash's mechanics imo, and could use a lot of cool stuff. He'd be my dream-char, but I'm not too hopeful since he isn't 1st party and Tails is more well-known as Sonics 2nd character. It's not impossible, but I'm not going to hold my breath on him. Still, he's my #1 wish Smash character.
2. King K. Rool
The DK franchise is too underrepped. And not just a little bit. K. Rool has been missing for too long now (even in DK games), and he's a really cool, evil and crazy villain with many possible moveset ideas from all his different appearances. But tbh, I'd be fine with just the crown-toss and everything else being "normal" - just put him in the game!!
3. Dixie Kong
Like I said above, DK needs more reps! Dixie more than deserves to get a spot on the Smash roster, she already did in Brawl.
Her hair could and should make for interesting move choices and it makes me a little mad when people think of her as a Diddy-clone, even though she could use a few similar moves here and there, but she doesn't have to. I really want to see her using her hair for grabs, maybe multijabs and most importantly her whirl (to glide). Her dashattack can also be straight from the DKC games. I've seen cool movesets for her as well with interesting ideas. She'd be a great character to add to Smash.
4. Waluigi
I was hoping for him to get into Brawl as well, though not as much as my top 3. He's the 4th "brother" of the Marios and would complete the quartett. It would just be really cool to have Mario+Luigi vs Wario+Waluigi or just generally all 4 of them fighting. Waluigi is a pretty cool, villainy guy that I grew to like a lot when he first appeared in Mario Tennis 64, a game I have very fond memories of. Such great cutscenes and emotion from Waluigi.
I had already thought about my top 4 before and it was pretty easy, since I've been wanting them for Smash since before Brawls release. So now comes the part where I have to think up my next choices..
5. Tails
Kind of a necessity for a Sonic fan to put Tails in as well I guess. He'd be pretty different than Sonic, though. With maybe a somewhat similar downB, but that's it. He'd be nice to have.
6. Shadow
What?! I'm a Sonic fan. Shadow is pretty cool and can be seen as a vaillain for the Sonic series. He could be like a semi-clone for Sonic. If you think about it clones are actually a pretty interesting concept, even if they share most of their moves. Similar characters with different attributes make for more interesting interactions/ways to play etc. He should have a few own moves (Chaos Spear instead of homing attack? And only downB spindash, give him maybe his teleport from Sonic Battle as a sideB, with a possible hitbox. This would be pretty similar to Fox I guess, but oh well).
7. Kabutops
I guess a pretty rare Pokemon to see on a Smash-wishlist. When I think of a cool Pokemon to join Smash I often think of Scizor (I remember seeing a Melee trailer and thought the Scizor from the Pokeball was actually a fighter, lol. And since then I always thought of Scizor being a really cool choice). But then.. do I really like Scizor? I do, but I like Scyther more. And who do I like even more than Scyther, who is kinda similar with his sickles? Kabutops. With a lot of slashes and also Water and Rock attacks he could have pretty cool and amazing-looking moves.
8. Lanky Kong
I guess you could say I got convinced for this one by a friend. He'd represent DK 64, which was one of my favorite games, so why not? He could have pretty interesting moves just by using all of his things from DK 64. The long arms would also be an interesting mechanic/design. Maybe be able to choose how far you want to extend them by keep holding a button etc. Would give him more range but more lag at the end or something (for grab/jabs and smashes only maybe).
9. Deoxys
I kind of started to like the idea of Deoxys since Brawl-speculation. The thought of being able to transform into one of 4 forms would make battles really exciting. He should be able to transform rather quickly, with just a little bit of lag (but no invincibility, if you hit him in his startup he can't change forms). His forms would kinda switch up his attributes and playstyle, which would be "balanced", "defensive (heavy and slower)", "speedy (weak)" and "offensive (strong but very frail)". It just sounds super fun and tactical. I guess you could somewhat compare it to Shulk, but to be honest I'd probably switch up even his moves a bit for his different forms, and make everything feel more "natural" instead of just "enhenced jump/floatiness etc", which Shulks Monado modes feel and look like to me.
10. ... Funky Kong?
I'm kinda running out of things to decide for. I still want characters in the game, but which one over which? It's too difficult to decide! But I guess I'd take Funky Kong.. I liked playing him in Mario Kart Wii... I started liking his voices and found them pretty amusing. Now that he'll be added as a new character in Tropical Freeze for the Switch it kinda pushes him again. Still funny voices (even though some nice ones from MKWii are missing xD), and well.. I did like him, in DK 64 as well. He wouldn't have to be limited to a surfboard. He could have some arms to rep DK 64 and maybe some other stuff (he's also known for his plane and boats, but dunno, I think the plane would be weird as an upB, so maybe he could use that as a Final Smash or something).
Still, the biggest reason he's on this list as #10 is (besides being a DK char) his voice.
Other characters that didn't make top 10:
Of course there are many other characters I'd like too see, like Bomberman (I actually wrote a little about him at first and wanted him in my top 10, but the lack of moveset potential put him here), Toad, Krystal, Wolf, Squirtle, Ivysaur, Banjo&Kazooie (imo lost their personalities when even many RARE developers left RARE and made their new own stuff with Yooka Laylee, otherwise they might've been #5), Ridley, Slippy, Shantae, Lyn and probably Decidueye (since he's a more realistic choice and would imo be the best rep for Gen 7), but I think I'd like my top 10 more than them.
To be honest I'm almost satisfied with my character-needs for Smash. Since Sonic, Mewtwo and Diddy are in Smash4 I was very happy (Mewtwo was super important to me).
Only the top 4 of my top 10 are what I truly need/wish for, with the rest of top 10 and the others as nice additional characters to play around with, but not needed.
Any of the top 4 joining would make me pretty happy. If those were in the game, I'd probably not really have a true wishlist anymore, since everything else would just be "nice", but all my faves would be in the game already, so I'd be happy either way.
Summary (if you really want to read more lol):
DK needs at least Dixie and K. Rool (I'd be really happy with even just one of them in the next game, but both of them would make the series feel more complete and it would really deserve it).
Other than that DK doesn't need anyone else imo (use stages/assist trophies/items for more DK stuff). Of course Lanky and Funky could be nice additions as well, but like I said.. not really needed for me.
Besides those I really want Knuckles and Waluigi.
I guess you could make a case for Tails, since Sonic & Knuckles without Tails could feel a bit... lacking, but eh.. he's just a little more important than Lanky and Funky.
Shadow would just be fun as an additional Sonic character to have in the game, but not needed.
Kabutops and Deoxys could be fun as playstyles. But I don't even like Deoxys that much as a Pokemon, so I don't care that much. Kabutops I do like, but since Mewtwo's in the game (just stay there!!) my Pokemon-needs are pretty much covered. ^^