A game like this is already in development, it's called Sword Coast https://swordcoast.com/
But of course I would love to have multiplayer. Just that, this game has already 100% geared its design towards the single player pause/click/pause campaign experience.
To add multiplayer, you'd have to go back to the drawing board and find a way to create a game play that does not need to pause, which means you would need to go back and rebalance all spells and all abilities. So basically I suspect it will end up something like Dragon Age inquisition's multiplayer? In the same time I bet you you could create an entirely new game from scratch taking the same amount of development funds, and design it with multiplayer in mind. Therefore you may as well just create a whole new game.