I am still not sure about the 4 mic blends using hypers. I know several tapers that mix hypers and subcards, and I just don't hear the advantage over a single pair of cards. Mixing a SD and LD pair of cards, or some shotguns with omnis, that would deliver something more distinct I think.
I'm going to side with Brad and earlier comments about hypers are for special circumstances and go one step further:
I'm still not sure about 4 mic blends when the mics are used
in the same spot. Putting a set stage lip and another set further back makes sense in the same fashion that doing a mix of board and room mics works; you are getting two distinct visions of the band, one is up front, the other is relaxed and warm. Puting two different flavors of mics in one spot does yield a different signature, but it's not nearly as beneficial (IMHO) as running them in different spots. I don't see a return on investment (in positive benefits) for the time and effort put in (in general, some special circumstances apply), especially outside of the sweet spot of a venue, but my values may not reflect yours.
Thinking about this further, really for a multiple microphone array, the issue really isn't about patterns and imaging and more about the sonic signatures and how different types of microphones compliment each other.
For the win (beat me to it by like 10 minutes while I was writing the above):
My question to the original poster is: What don't you like with the 4021s that you are trying to change, and what specifically about do you
not want to change? Mic blends (or blends in general really) bring some good, but equally bring some bad so one thing I'd look for is two sets of mics where there are few things I don't like about them, and then look at what positives each has, and then consider experimenting as such.
An example would be; "well, schoeps have this beautiful sound, and neumann's color and texture make guitars rock, so they must be really awesome together cause they are just awesome seperately", but what you also get is "schoeps mud with the strident (and IMHO misplaced) presence bump of neumanns" in the same mix.