Nicholas:
The ten flashes indicate "in theory" that there is a problem with ROM U27. The issue is that the self diagnostics are not always accurate, and the problem may not actually be the ROM itself, but associated circuitry, including PIA's.
Battery damage is elusive, because it causes all kinds of unseen problems - and also creates shorts, because the battery "liquid" is conductive. It really requires a stripdown of all parts that were affected by the leakage to remove all possibilities of interference. It can even be a socket issue!
I have a board right now that is giving me 11 flashes at boot up (meaning a "U26" ROM problem), I plan to look at it today. I will let you know what I find.
Chris