The firmware that Mercury provides is the same firmware for all of the Mercury OEM partners. So there is no need to flash different firmware to the boards when changing over the host software to a different OEM provider.
The only thing unique to each partner is that when the boards are ordered an OEM code is programmed into each board. Each OEM partner has the capability to program their own OEM code into the boards, but not all take advantage of this. You would need to check with the OEM partner to see if they support this ability.
The OEM codes control the look and feel of the web configuration pages as well as the OEM factory default settings. The host software also can validate that the hardware coming online with their software has been programmed with the proper OEM code.