If you change the tone of the game world, what other "classic elements" are even worth keeping? Put another way, the whole reason Mask of Eternity is considered a failure in most fans' eyes is because it didn't "feel" like a King's Quest game. And a HUGE part of that is they darkened the tone and took out most of the humor (among many other things.)
Putting a bit more seriousness (I stress "a bit") into the story / world with the rest of the elements that we have come to associate with the series does not equal a clone of MoE.
I don't think my suggestion is too extreme... the stress is still on item hunting / puzzling and exploring the realm of Daventry, not action. Hell, action (in the MoE sense) won't even have to be an integral part of the game.