As long as you de-solder the two wires going to the jack socket, you can take the whole wiring harness off a Strat just by undoing the pot nuts and pickup screws etc. You can then de-solder the other wires away from the pickguard if you are worried about damaging the pickguard with heat.

However, I often find it better to re-wire everything with the components re-attached to the pickguard. I use vintage-style solid push-back wire, which is easy to bend into shape and wire everything very neatly - which is not as easy to do if you use a cardboard template to mount the hardware on first before transferring the whole harness to the pickguard.