I know what your thinking:
THERE WILL NEVER BE A SONIC MMO. A WORLD FULL OF SUPER-FAST HEDGEHOGS DOESN'T MAKE SENCE!!!!
You finished? Here my idea for a good Sonic the Hedgehog Online!!!
Ok first of all, you will not be a hedgehog, you will be a human. You have to raise chaos for battle. This closely resembles Neopets only way better.
Now your asking: Besides chaos, what does the game have to do with Sonic?
You will be Sonic and all other characters (including Tails, Knuckles, Amy, Cream, Big, Rouge, Shadow, Espio, Charmy, Tikal, and Vector). You will be these characters in 1p mission (meaning only you are in them and the only things moving are NPCs and you in the mission) for rings to buy things for your chao. You see other players as you walk around adventure-fields (yes thats off Sonic Adventure DX). In the adventure fields you can find portals for you to go to the missions.
In the game you can have your very own chao garden, using ring to buy diffrent landscapes, more room, and other things (like swings or a rock). As your chao progresses, it will turn into a hero chao or a evil chao depending on how you raised it. Also, you can get more chao eggs by letting your chao mate with someone elses chao, or buying a new egg.
A sonic mmo would be interesting indeed, unless you didn't play as a sonic character but rather gains abilities depending on your starting equipment.
I.E say i started out with a tail, eventually i could play
or if i started with speed shoes(+10% runs speed ect) and just keep leveling and by like level 70 lets say he will have his max speed as a usable ability.
sounds good, but tones of people running around as sonic characters would be a bit...idk. you could have the sonic characters in the world, and they could give out quests and help you. You could even do quests with them along side you. Here's an idea.
You can create your own animal/human thing (weather it be a hedgehog, echidna, fow, cat, duck, bird, snail whatever the freak you want), and costomize it to make him look like no one ells (CoH/CoV costom system would be required). then, you'de pick it's type, power, speed, or flying. each would have special skills that would help you get past dungeons and obstical s in the world.
It would probibaly have to either be like lunia (a place in the middle that every one meets at and buys equipments, then make the rest of the world map based with levels, or a traditional attack, wait, skill, wait settigng with a word map and dungeons. it would either end up looking like a sonic themed dragonica, only faster paced, or just a 3D sonic world with monsters and all the works.
I'm not objecting to a chao pet system you could raise and let fight beside you, it would acually be fun catching the animals from quests and monsters and feeding it to your chao to make it look different. but it doesn't need to be the core of the game.
There could also be minigame you could compete with people in like hoverbording, or the traditional catch the emerald. That's what it would be like if they made one, or at least that's how I would make it.
Three types of people: Speed (Sonic, Shadow, Espio, etc), Power (Knuckles, Big, Vector) and Flight (Tails, Rouge, etc), but you could just get to choose different animals and change their appearances with City of Heroes detail. It could just be a roombased game with constantly updated maps that are randomly generated. Throw a little Chao to the side with chao battles and races like back in the Dreamcast.