A reader wrote me after having loved the turn-based combat of King's Bounty with the question: "Why oh why couldn't this be integrated nicely into a MMO?" The idea being that the general part of the MMORPG would run in real-time, but combat would be turn-based.
If you think that is impossible, I have to point out that this already works quite nicely in Wizard 101. Of course players don't get all that much time to complete their "turns", only some seconds. But between having to react in fractions of a second, and getting 10 seconds for your turn, there is a huge difference. The main advantage of turn-based combat is that designers can't hide their trivial combat moves behind the "challenge" of twitch-based combat; in turn-based combat players need to think more, and get the time for thinking.
Turn-based, tactical combat works best if you don't just control a single character, but a whole army. Again, that does exist in MMORPGs, for example in Atlantica Online, albeit without the troops moving over the battlefield like in King's Bounty.
So, in summary, turn-based MMORPGs seem to be possible, but the examples are few and far between. In fact, turn-based single-player strategy games appear to be nearly exclusively be produced in Eastern Europe these days, with the rest of the world creating rarely anything but real-time strategy games. So turn-based games in general are evidently a niche genre, and turn-based MMORPGs even more so. A pity! If you know any good turn-based MMORPGs, I'd love to hear about them!