The 4 digit Firmware V1 code should already work with it if you want to go this way. Normally I'd like to help you with it, but I've got a load of new releases coming up, so I don't really have much time to help at the moment.
I would appreciate it if you could not start selling it: I'm a bit sensitive to this, because I had the first support request today for a ripped off board, and it's a real mess. Someone has taken the schematic and just stolen it without understanding it, I'm going to have to start asking people for pictures of their boards before I give support, and that just sucks. The worst bit is that the rip-off layout is really, really bad.
well, with the firmware V1, we have two free GPIO pins, and one of these is for a PIR, so in reality it does not matter very much if you make it from the basis of V1 or V2 firmware. In the next few days I intend to also put the PIR code into the V1 4 digit, and that will work with all clock versions.