Yeah, an interesting cross breed for sure. And about time someone did it. The K67 has the well-known (deliberate) frequency rise that has to be corrected in the circuit. Some attempts have been made to tame the capsule itself. This can be done to some extent, still flat it is not.
A K47 hole pattern, but with a double backplate seems like a nice "best of both worlds" solution for many of the more straightforward and/or flat plotting circuits. Theoretically, I'd say it couldn't sound exactly like a K47, if only for the phase shift from the double backplate. But I do believe that with some proper hollering this concept could be a hit. Already I'm dying to hear the thing in a C12 circuit. Just one example.
Eric, is there any chance you could come up with a frequency plot?
Henk