The question is, why would you want to work the way you discribe? i understand what you want to do, but not why. And it's the why that's important here to help you out..
1 - As a PC connection is quit a simple 1 way connection, that's simple to make, ( as you only have to have a "MONO" audiojack to do it - if you take a stereo audio jack that would be a bit more complex to solder, not that more but you'll have to look more carefully).. Just take a PC with cut of the 'male' part and solder the + and - to the + and _ from your Audio jack ( MONO)
that wouldn't be a good idea, because the "digital back" needs at the end of its latency, ( or to now when to end its latency) a "sign" the image has been made. And phase one ( not hasselblad, as you can set exposure times in the back) uses the shutter closing for this. What happens when the shutter closes is that the "flash" synchro connection is freed again, and then the back assumes the image has been made.
If you realy want to do it, you would have to make a By-pass of the pocket wizard, ( just like the kapture group bypasses the latency wake shot) . that's not that difficult to make only need the correct components and a good solder pen.
If you want for some reason to "end" your exposure before the actual shutter closes ( and thus use your back as a shutter) i could only see this work with long exposures, and then the "solder your own cable , link to pocket then to phase, system could work.. But why? ..
I don't see exactly why you would want to do this, as there is a flash sync ( X , or female PC connection) on your back.
Connect the Lens shutter flash sync to your back via the phase cable, ( or capture groupe), and then connect your pocket wizard to your back, Your pocket wizard will sync exatly on the same time as it wold on the lens ..
If you want a "retard" function , you can to this with the Pocket Wizard functionality ( if you have a multimax or similar) ... This way you can also flash sync at the "end" of your exposure instead of the beginning..