You might try www.guitarnuts.com. This guy has a lot of good information, and while your exact question my not be answered there, I think you'll still find a lot of cool options you may not have considered. Good luck.
I do that on most of my guitars, including my strats and my Tele. I use one volume control on the neck/middle pickup, and the other as a master volume. On the Tele, I do without a tone control.
In my arrangement, the 'volume' control for the neck and or middle pickup is more of a 'blend' control. I use it to vary the 'mix' of the pickups when the neck and or middle pickup is combined with the bridge pickup.
Whew! Zander - sorry about taking so long to reply - I haven't looked at this thread in ages, obviously.
There probably isn't a diagram anywhere on the 'net for it - It's a variation of something I came up with for my two-pickup guitars - I call it the Rick Circuit - Click Here - On my neck-through strat, the blend control (second volume) controls both the middle and neck pickup. On my blue MIJ Squier, I have the middle pickup completely disconnected so the extra volume control is wired just like a Gibson-style implementation of the Rick Circuit.
When I get home tonight I'll pull the back cover off my neck-through strat and see if I can draw up a quick diagram for you.
EDIT: UPON FURTHER REVIEW... I misled you. I apologize. When I got home and opened up my neck-through strat, I found that the extra volume control only controls the middle pickup, not the middle AND neck pickup. The reasoning was the same - use that control as a blend knob when I'm using either the bridge/middle combo, or the middle/neck combo. The middle pickup lead goes to the volume pot first and then to its normal spot on the switch.
I still think it can be done, but I need to get something straight - do you want the middle/neck pickup volume control to be completely independent of the master volume?
Like, have one volume control for the middle/neck pickups and a separate volume that controls the bridge pickup, or...
Have one volume control for the middle/neck pickups and then an overall master volume for the whole guitar?