flashing 5700 with custom bios is not a problem any more

the only problem is bios editor for Navi... hexeditor is our friend and
shostt58 
Please define yourself.
AFAIK, flashing a modified vbios (except then flashing an XT vbios to a non XT card) does not work due to the on board PSP basically saying "Nope".
Using a custom softpowerplay table, that is of course possible.
So not sure what you're trying to say here.