Unfortunately the only QD return to zero mount for the MP5 is the ARMs and factory HK claws mounts. I used to use an aimpoint on an ARMs claw mount and I found that it placed the reticle way too high for my tastes. Plus if you are planning to remove the mount fairly often, be aware that the thing will eventually tear up the gun. You won't be able to cowitness with the ARMs, but there is a backup 'tunnel' that you can use your irons through, although obscuring a lot of your sight picture. The ARMs mount is just as good as the more expensive factory STANAG mount but much cheaper ($150), but I think there are some airsoft clones out there, so make sure you are getting the real thing.
B&Ts are a better mounting option IMHO because they place the reticle much lower to allow for proper cheek weld. The problem with the B&Ts is that there is no QD feature, and no return to zero since they are held on via 4 allen screws. I used to use the low pro B&T, and it works well, and allows cowitnessing (with the low aimpoint ring), BUT it was getting dinged up by ejected brass. This concerned me a bit, so I ditched it.
My current setup is the best of both worlds in my opinion.
B&T 21262 with ARMs #22M68.
It gives extra mounting real estate and the ability to use ARMs QD rings (the ARMs does not fit on the low pro).
I does NOT allow cowitnessing, but still places the reticle low enough for proper cheek weld. And with the QD ring, I can quickly dump the aimpoint and switch to irons if I need to. So I can just leave the base on the gun 'permanently' and keep my zero, while having the flexibility to shoot with irons or the aimpoint with a flip of a lever (ARMs).
This is a bit more expensive of an option, because you have to buy the mount ($150) and the ARMs ring ($80) but I think it is worth it.