OMG. I would love a Blizzard fighting game! Blizzard and NRS teaming up: awesome character design with awesome fighting game design. I've always wanted to play as Sylvanas Windrunner in a fighting game. Sylvanas vs. Kerrigan? Tyrael vs. Thrall? AHH!
But, yes, they should also make a new game with original character designs. Their creative design team is top-notch and should be recognized for their own characters and stories beyond Mortal Kombat.