The simple answer is that the relays can not be programmed to be open instead of closed when the output receives the ON command. I have been considering some ideas that may help you out though.
There is still a way to use the 2X4 with an external FET and relay, but that may be more than you want to tackle.
Another option is to leverage the EZBridge macro capability. You can have it set the relay to whatever state you want when the switch is turned on (i.e. disable the motion input), and enable the motion input when the light is turned off.
This will work with a manual activation of the light and when the motion sensor turns the light on. In both cases it is disabled from the 2X4. After the light turns off, it is enabled to the 2X4. May sound like a sales pitch, but you can do some very complex behaviors with the EZBridge. What you would loose with this solution is the reset of the timer if motion is detected during an on period (may be an issue?).