I'm glad to hear about the Wimberley offering. I contacted their customer service once before, and they stroke me as good people to do business with. Regarding clamp models, keep in mind that the C-10 is discontinued, the C-12 is the current model and what I've had for almost a couple of years (http://www.tripodhead.com/products/qr-clamps-main.cfm). I can attest that the C-12 works fine with Kirk L-plates for the 6D and 7D.
You seem to already be on the Wimberley track, but you mentioned liking the lever system. RRS has a lever clamp that also has anti-twist groves. I ignore if they will retrofit your Z1, but a quick phone call can help (they have great customer service too).
Definately agree on the Wimberly comment. I'd do business with them in a heartbeat and in fact their BH-300 is going to be my next ballhead. My fiesol just isn't cutting the mustard, and it even locked up in 100 degree (F) weather. so I'm done with cheap ballheads.
As an aside, Wimberly does not put a C12 on the Z1; they put on a C11 which is specifically designed for the Z1. Reason being: C12 is a brand-agnostic clamp with setscrews that can be installed on most any ballhead. C11 has been designed to take advantage of the anti-twist nubs manufactured into the Z1 shaft itself, so it has no set screws and none are needed. I'm also told that the top-side groove pattern is different, though I'm not sure why that is. So bottom line is that the C11 is functionally equivalent to the C12. one can certainly put a C12 on a Z1 thats for sure, but Wimberley doesn't do it.
Whats curious to me is that Arca Swiss, if you contact them directly, will tell you if you want to put an RRS clamp on, then buy the 3/8" stud / platform flavor of the Z1 and screw the RRS clamp directly onto the 3/8" stud. Wimberly told me this is not a good idea, and that its better to take the platform off and install the clamp onto the ballhead shaft itself. I'm sure the RRS clamp supplied with an M6 screw will work well in that situation.
The issue here is "does AS lock down the platform in the same way that they (reportedly) lock down their own clamp?". We don't know, but one thing I do know is that the Z1s supplied by AS to Wimberley are not locked down. Wimberly takes the platform off and installs their C11 as I mentioned above. Moral of the story is that if you want a no-DIY solution, the Wimberley BH-300 is the only way to go, and there is zero worry about breaking the thread lock. alternatively, if we can verify that AS supplies the Z1 (with stud and platform) via normal channels (i.e. B&H) without thread lock, then field replacement with the RRS clamp would be quite straight-forward and DIY friendly, as many have already done, prior to the recent "AS clamps are locked down" discovery.
ONe other interesting detail I"ve learned is that apparently AS may be starting to ship Z1s with a conventional single-decker clamp. Word from Wimberly is that this stock may be still emerging and that B&H for example may still be shipping the double deckers. to be sure, their photos still show that. So I dunno on that one...