Interesting question: What's the minimum visual obstruction possible for this specific type of setup?
I assume you want this to be mountable on a conventional mike stand, perhaps via a 3/8" threaded socket.
I'm interested in this as well. Might be a nice project for someone with a 3-D printer. There are also some pre-existing Schoeps parts (e.g. "SGC" stand clamps) that might be used to make construction easier.
But there would need to be a variety of models for different angles between the axes of the capsules, since that also affects the distance between the "holders". Cardioids at only 90 degrees--bah, humbug! 90 degrees is for figure-8s. The -3 dB point of a cardioid is nominally 131 degrees from its main axis, and life begins at 120 degrees as far as I'm concerned. With "quasisupercardioids" such as the MK 41 (which technically is between super- and hypercardioid, but considerably closer to super-), I'd want the angle to be 100 degrees or even a tad more.
--best regards