Make potion of literacy better for characters with literacy.
as above.
If you don't have literacy, the potion of literacy is pretty nice; it gives you the skill and bumps you to the 60s or so--not great, but good enough for most purposes. I recently got it on a character with 19 literacy and had my literacy bumped to 36. To say I felt cheated would be the understatement of the last two hours.
I think if you have literacy, the potion should probably bump it to 100, or at the very least, bump it to the 80s or 90s. It's not like this is overpowered or anything, and it should definitely be better than getting it on a character with no literacy.
P.S. changing how it works for characters with no literacy would be the wrong decision.