So, I've been thinking about the MOBA scene. More specifically, I've been thinking about League of Legends.
It may come as a surprise to... nobody... that League of Legends is not my cup of tea. I don't much like competitive games, and I don't generally have the time to dedicate to actually playing a real-time multiplayer game.
But League of Legends has a dedicated core of fans that really love it, and some fairly brilliant little gameplay bits. In short - like it or not, League of Legends is a good game.
Could you do the same kind of thing in a cooperative game?
Let's start with the cooperative battle.
Let's start by flat-out lifting the combat system. Except that there is no enemy team. Instead, the heroes fight against an automated threat.
A lot of players instinctively recoil at that statement. The big draw of a MOBA is the fact that you fight other players. But, hey, I didn't say anything about not fighting other players. I said "automated", not "stock".
Let's go ahead and presume that the missions are created by other players. The players can place the opponents. Let's just run through a quick example of the basic idea.
You have to defeat the end boss (the final lair) to win. There are several paths that lead to that lair, but along those paths are lesser lairs you must enter first. Once you enter a lesser lair, you awaken the monster inside. You can get past, now, but there's a heavyweight non-generic monster making trouble. Even if you kill the monster, it will eventually respawn as long as the match continues.
Fundamentally, the matches are likely to still remain very much like a MOBA match, although the pacing is completely different. The part of the enemy team is played by an ever-increasing roster of heavyweight monsters.
There are a few advantages to this system. First, it's robust about griefing and substandard player action. That is, the enemy can't screw you over by disconnecting or whatever. The whole mission is laid out ahead of time on the server, so the only people actually playing it are all allies. Your allies could still grief you, but that's a different category of problem.
Second, it cuts the player synchronicity requirement in half. You no longer need 10 players to play a match - only 5. Still, you can actually go the opposite way. Since you don't need balanced sides, you could play an allied team with 12 players in a kind of "raid" format. It allows for a wider variety of easier-to-start matches.
Third, it creates a new kind of gameplay: creating quests. A lot of players enjoy creating. It's compelling to express yourself by placing various monsters and challenges. It's doubly fun if you can watch the replays of people trying to tackle your map. Sure, there's always a risk of dongs being drawn, but compared to the general chat in a MOBA, that's a pale shadow of a problem. In addition to being a compelling form of gameplay, it's highly asynchronous (you can do it on your own, even offline) and also a great source of revenue (buy special challenge elements in the cash shop).
Now, this would have to work via a balancing/ranking system. So the player who makes the quest has to put some kind of ranking guesstimate on it. Players who challenge at a given rank will pull randomly from quests near that rank. Every time the players fail, the quest's rank goes up and the players' ranks go down. And visa-versa. The player who made the map gets some kind of kickback every time players challenge his quest, but only so long as the quest's rank remains near his original estimate. If the quest turns out to be much easier or harder than he thought, the quest remains in rotation at the new difficulty level, but he no longer gets any gold. This should keep rank griefing/farming to a minimum.
Another big element of popular MOBAs is the persistent part of the game.
Part of your persistent world is which heroes you have unlocked.
Some of the persistent stuff comes from tweaking your combat loadout. Although each hero is always the same, players will tweak their abilities slightly with different global/generic capabilities. Part of your persistent world is which abilities you have unlocked. In this case, that would also involve which quest construction elements you have available to place.
Part of your persistent world is your rank and history inside of the combat system. In this case, that would also include constructed quests.
In a cooperative game, it would be wise to add in some connectivity in the persistent game, making it vaguely social. Guilds and so on are common, but in this case something more tangible would probably be wise.
I would probably make a kind of simple "kingdom" game, where you have various lands you can tweak via a casual play interface. You know the sort - upgrade by clicking after two days, or click each hour for gold. Change whether that field is growing daisies, horses, or farmland, etc. Your kingdom could be a big part of what general upgrades are available to you. Also, you can customize some features of your kingdom (such as your ruler, crown, flag, maybe castle interior, etc) to express yourself, and those customizations may also be affected by your kingdom's resources.
You can make your kingdom larger by winning in quests. Higher-ranked quests give you a lot more kingdom land than lower-ranked quests - more than linear. So you want to fight in the upper tiers if you want more kingdom.
A lot of players aren't going to care about the kingdom stuff, which is fine. You can become either an ally or citizen of another nation. As a citizen of another nation, you don't have lands of your own. Instead, you have a manor house in the leader's nation. Lands you earn by fighting are given to the overall nation, and they are governed by the ruler and any governors he appoints. All you need to do is fight to your heart's content. The general abilities and/or heroes which would rely on your nation's development instead rely on the overall nation's development.
If a kingdom has citizens, you'll see the player avatars bumming around in the castle all the time.
I think there's some opportunities here. It sounds like a fun game.