I've battled this concept for about 5 years now and have owned/tried several of the available options.
Key Points:
1. I don't see the point of folding rapid transition sights. If I need to transition rapidly, flipping sights up is counterintuitive.
2. I don't see the need for the complexity of an A2 elevation drum on the rear. The Surefire/Duek units are overly complex and heavy.
3. I don't place a huge premium on cheek weld for rapid transition sights. Whether I'm coming from a low ready/search position or getting out of a magnified optic (ACOG in my case) to deal with an immediate/closer threat, a more heads-up, situationally-aware position is preferred.
I thought the XS sights would do it for me with their open design. However, they are too low. No amount of cramming my face into the stock was going to get them to align properly.
Thoughts:
1. @Tom_Jones: How feasible would it be to make a plate that would mount to the RMR screws on an ACOG, but that would extend forward over the optic (roughly the length of a G17 slide) and then mount a set of pistol sights to it. The screw-in front is probably the easy-part. The dovetail in the rear is where things would get complicated. Here's a ROUGH sketch of the idea:
2. Refute any of the above objections about existing designs.
3. Any other ideas?