Benefits from making a separate game from a MMO. (A standalone game with a different revenue model that also spreads the franchise).
- They already have a workable engine; combat, movement, abilities, classes
- Bosses, Noteworthy NPCs, or even Beasts could be playable characters.
- Place for free-to-players with cosmetic shop. Revenue for more programmers working with the engine.
- Variety of map objectives; ctf, plots, a mixture of PvP and PvE, and a version of DoTA's original lane game.
- Skills could somewhat translate between the genres.
- Balanced gameplay for free and paying players.
- Sell customization (use armor already in game!)
- Earn points in-game to purchase new playable characters
Basically Modding the Game
If it's not beneficial for developers to make the modifications needed, the gaming community could do this if they were allowed. Warhammer tried something like this with Wraith of Heroes, which started off very well but a EA cash shop ruined the fun.
This may even allow the studio to hire more developers. Working with the engine would familiarize more programmers with the original MMO, and even if the MOBA is horrible they could make a small profit. I would love to see someone like Anet try this with GW2 - with a perfected version of their target aim mod - plus GW2 is such a small jump to MOBA. Even older games like LOTR or DnD could explore these options.
It doesn't even have to be a MOBA. As open as most MMOs are, you could basically make an endless amount of standalone games. I do understand some developers don't own the engine and would have to buy another license. There could be other problems preventing this from happening but I think there is great potential in reusing code and funding a larger team.