To be honest I'd rather have the lux scene files and the png in a dedicated folder anyway.
Can you allow us to set a destination folder using the GUI? That'd be my preferred solution anyway.

Software: OS X 10.8 - Poser Pro 2012 SR2 - Luxrender 1.0RC3 - Pose2Lux
Hardware: iMac - 3.06 GHz Core2Duo - 12 GB RAM - ATI Radeon HD 4670 - 256 MB