The WSSI module is only able to be used as a dedicated "monitor" mode module. The config guide:
http://www.cisco.com/en/US/products/ps11983/products_tech_note09186a0080bed15d.shtml#conf
states that...
"Note that the WSSI module is only active on AP3600s configured in either Local Mode or FlexConnect Mode. The WSSI module is disabled in all other modes."
There doesn't appear to be any way to configure the "mode" of the WSSI module itself and anything but Local or Flex on the 3600 would disable the module. The module is intended to provide a dedicated radio to offload all monitoring features normally part of Local mode off-channel scanning operation or ELM: CleanAir, RRM, Rogue Detection (not detector), Location/Context, WIPS, allowing the primary radio to service clients 100% of the time, while the WSSI performs all other tasks.
You may want to contact Cisco TAC or you SE for confirmation and perhaps request that a feature enhancement bug is created.