Does anyone know if something like this has been done? The concept I'm talking is essentially a fighting + rpg hybrid in that you design your own character and spec them in various ways as you level up (different fighting styles? different martial arts? schools of magic? superpowers? take your pick), and then play off against other characters of similar levels in the manner usual to fighting games like mortal kombat or injustice. It would be massively multiplayer in that you could participate in various tournaments on a constant basis against other players/ai, levelling up till you reach the cap, at which point the game becomes about trying to rise to the top of the fighting world by winning as many tournaments as you can. A pretty large amount of content could be imagined - contests with different rules, contests where you're only allowed to use moves from one fighting style, and obviously player created content given the multiplayer nature of the game.

Honestly, just describing it it's far beyond my reach in terms of actually developing it, but i cant help but be intrigued as to whether it's actually a new idea in any way, or whether im just describing some obscure/not-obscure-at-all-why-havent-i-heard-of-it game

Can't think of any mmo-style fighting games, but you should ask yourself this question whenever you have an idea no one has tried before : Why has no one tried that idea before ?

Usually the answer isn't that no one ever had that idea before, but rather that it's simply not a good idea. Or not a feasible one.

Typically, what would be the advantage of a mmo-style fighting game over a regular multiplayer fighting game ? I can't find any, you will only dilute the gameplay that people want from a fighting game with tedious less interesting gameplay. Bringing rpg elements to a fighting game means you are creating unbalanced fights, which is game-breaking for a competitive fighting game.

its true that it would be harder to balance - but with a broad enough specification tree, and player creativity, you'd think player combat styles would vary enough to provide interest? also the aspect of customisation is usually a huge pull in any game. It's one thing to rise to the top of the ladder and its another thing to rise to the top of the ladder playing as a character YOU designed, with a skillset YOU chose - i feel like that really increases the sense of accomplishment? honestly though i dont know enough about the balancing of fighting games to know whether introducing the variety needed for interesting gameplay would make it completely impossible to balance, but it's an interesting thought

It will usually end up with everyone following a meta that changes with your continued balancing of the game. No one would choose customization over competition. That's how it works in every single competitive game that involves rpg elements, look at MOBAs for a perfect example of that. Fighting games rely on reflexes and knowledge, it's all about executing combos correctly, they are speed and dexterity games, very different from rpgs and they attract very different players who are looking for very different types of gameplay. Just because customization is usually a good thing in RPGs doesn't mean it would work well in other genres and with different types of players.

Fighting games are skill based games, with almost no other factor; making it the most difficult genre to turn MMO.

The problem you have is lag. While a major problem in most games, it's a nightmare in fighting games. The predictive solutions we have for lag doesn't work well in fighting games where players can stop a action and counter others.

Most fighting MMOs that do exist and work are team based, like the old double dragon games. With players fighting NPCs alongside each other.

There is also a few where player vs player is the aim, however they keep things very simple. There are lots of Free to play ones, so try a few.

Turning a fighting game into a RPG is extremely difficult. The recent Batman games and the Witcher 3 are the most successful at this.

Both games simplified the combos to single button presses and still players mostly just use the primary attack.

Even if you did not mean that kind of RPG, only the xp system and such it will still reduce the amount of combos a player can learn.

The Devil may cry games is the best example of this. When a player can only use a skill once unlocked it takes them a lot longer to become adept at the skill than if it was available from the beginning.

You would think that keeping combos locked until the easier one is learned would aid in learning the combos, instead it hampers the learning.

immediate controls and pvp-online-multiplayer sadly don't go along well for reason already described above. tanks/spaceships/cars, from a tech-perspective, simply serve as an excuse for delaying the player-actions enough to hide lag. fps games scratch the edge with one player getting the disadvantage (usually the player being shot at). but like direct face-punching-action without frustrating delays, and fans of face-punching-action count delays starting with 0 frames, would likely remain an idea until global/national pings have been lowered considerably.