The blessed potion of gain ability still only grants one attribute point, but it allows the player to choose which.

Define a new set of ability score maximums which represents the highest the score can reach via exercise. These caps are always equal to or higher than the existing maximums, which represent the highest a stat can be increased to through potions of gain ability or other stat-boosting effects. In some cases, the exercise maximum should stay the same and the non-exercise maximum may need to be decreased.

It’s an open question on whether restore ability should be able to restore points to their exercise-only maximums, or just up to the gain-ability maximums.

Give potions more side dipping effects:

• Dipping an eroded item in a healing potion repairs erosion on it; 1 level for regular healing, 2 for extra healing, and 3 for full healing. Restore ability will repair all erosion as well.
• Dipping a negatively enchanted item in a restore ability potion reverts it to +0 if the potion is blessed, adds 1 point if uncursed, and does nothing if cursed.
• Dipping an enchantable item in a gain ability potion enchants it (by 1 point, always).
• Dipping an uncharged item (possibly excluding rings) into restore ability has the same effect as uncursed charging it. (Blessed charging cannot be reproduced this way, even if the potion is blessed).

Dipping a blank scroll or spellbook into a potion of gain ability turns it into some random scroll or spellbook. The beatitude of the resulting object uses the same formula as magic markers. Could also do this for wands of nothing, which become some random wand, without changing their charge count.

Cursed potions of gain ability give you an ability point in something by taking it away from one of the other scores.

Blessed potions of gain ability allow you to choose which stat to increase. Possibly, since this would ordinarily be a nerf, max that stat or give you a few points in it.