I would highly recommend Rogue's Pacman strain for this purpose; it's clean and finishes malty and replaced the lager yeast that Rogue used to use for Deadguy.
I've really been considering doing a number of beers that use english malts but lager yeast and German hops, and german malts but english ale yeast and english hops.
I think an english dark mild ale grist fermented with a lager strain and a munich dunkel lager grist fermented with an english ale strain would be pretty interesting. -Especially targeting a 4.5% ABV ish gravity for each. I think you could produce a VERY passable and interesting dark mild and a very passable munich dunkel this way. (Might have to decrease the gravity on the mild to 4.1% ABV, though.)
-I also have to think that a 3.9%-4.1% ABV dark mild ale could really benefit from the increased maltiness of a decoction although I'm afraid that it would increase attenuation, which would NOT be good for a mild...