What suitable tools are able to accomplish this task? Is CodeRush’s UEFI Tool suitable for this task?
AFAIK andyp’s PhoenixTool (>LINK<) is able to do it.
You should either try it or ask the tool maker CodeRush himself.
UEFITool is a generic utility, so you can try to use it for replacing OROMs and adding GOP driver, but only if you understand how the original OROMs/VBIOS work on that Phoenix BIOS. I don’t have any Phoenix-special routines in UEFITool and I don’t plan to include anything related to OROM updating, because I don’t see the problem that one can solve with such updates. If you want it - I’m waiting for your patches.