Currently i'm implementing USB in my WICED application in combination with a STM32F412RG. However, the WICED delivers an old Standard Peripheral Library which does NOT have support for USB. On the website of STM I found a STM32F4 USB library. Unfortunately that library needs the latest HAL LL library.
When is WICED going to renew the STM32F4 Standard Peripheral Library to the latest HAL / LL libraries? Working with SPL from 2016 is old.
Unfortunately, there is no plan as of now to update the Standard Peripheral Library to the latest HAL LL libraries for STM MCU in WICED. As per your requirements, you can use Mbed platform. The integration will be easier in Mbed, else you can use WHD in STM IDE.