I noticed this thread, and it peaked my interest, I'm new but I do have some input. It seems that your going with, or leaning to a Warp feed, and some kind of Railing for a Reflexive Scope. But this clearance thing is raining on your parade, for some ideas, I'm into airsoft and paintball, but they have elevated Scope Rails maybe you could use.
For Copy Right purposes they won't allow me to provide a direct link but.
http://www.redwolfairsoft.com/redwolf/airsoft/Category go under where it has listed AEG/AEP, scroll down to "Accessories", and then on the other browser to the immediate right , go to "Scope Rail & Mounts" I have an G&G GR16, possibly a CA M15A4 soon, I was thinking about attaching a ACOG to the top of my S.I.R. and I realized I still want to use my Iron sight, so I'd have to get an elevated Scope Rail, to still be able to use my Iron sights, and use the Scope, because I took off the Carrying Handle.
P.S. I'm probably going to get a TAC-ONE Soon, it's a great weapon, and similar to my M4 in specs, the Selective Interface RAIL system I have on the foregrip, etc.
EDIT: If this does help you, I have hundres (literally) links to para-military and military sites, I can help you track down something to mount on the common 20mm accessory rail which appears to be the dimension you'll be using.