it should be done the way namine has mentioned, at least temporarily, as basing off an individual stat will ultimately discriminate against certain classes, and as such, certain builds will be favored over others.
it sucks bad that bAtkRate is borked like it is as it'd make things oh so much easier.
i know i personally don't feel like digging through the code to find out what the issue is when it's probably already been addressed by eAthena and is in a newer SvN that we just don't have yet.
i don't know for sure, but would it be possible to have it check the atk power of the weapon you've currently equipped and be able to give a bonus based on that to you attack value? or would you still have to end up using bAtkRate to make the adjustment to your overall atk power?