I hope you don’t need to dig quite that deep. The WICED SDK provides the WiFi drivers, but only as a binary image which is uploaded to the BCM43362 on startup, so unless you know the internals of the BCM43362 I’m not sure how much you’ll be able to reprogram it.
How low-level is the WiFi functionality that you’re looking to implement? Is the functionality provided by any of our current WiFi APIs, either at the WICED level, system firmware level (in the HAL) or at the Wiring level.