Mercs and Street Fighter 2 Turbo are both CPS1 boards, not CPS2. If it was CPS2 then that suicide battery would make things more complicated than just a simple eeprom switch.
But yeah, you can probably just buy a HF board for around 20 dollars from someone here on the forum or over at shoryuken.com. A lot easier to do, and you wouldn't have to destroy a the other board. MERCS was probably produced in a lot smaller numbers than HF.