Li Shenron said:I'm all about supporting a player's creativity as much as possible... but there are situations when it could possibly make a precedent that you later can't easily get rid of. Two examples coming to my mind are (1) allowing to use a leather strip on the weapon to drop/pickup as a free action, (2) allowing to store wands or small weapons in your belt to draw/sheath as a free action.
As you see, I'm not very confident when it is about changing the type of action...
There are already precedents for what you say and for drinking a potions.
Check FRCS for the bandoleer (I believe) it allows the storage of some number of tiny items that can be drawn as a free action. Dragon came out with an article last year that had a bunch of innovative items, one being a potion helmet - had protective compartments connected with tubes that allowed you to drink potions as a free action (I think it stored 6 potions).
If you have ever been to a fraternity party you'll know that 1 ounce is an incredibly small amount. I personally could chug at least 2 cans of beer in 6 seconds, and I am not all that good at it.
In terms of quantity, there is not contest here, the volume of 3 potions should not be an issue (and let's not have the ridiculous dicussion about a feat called "Chugging").
The question is one of game balance. If you are concerned about game balance, simply rule that simultaneous consumption of potions ruins them. I would add the caveat that this only applied to potions of different types. This means that healing potions (of the same type) would work together. I think of it this way: a enterprising brewer might have the not too brilliant idea that it would be more efficacious to create potions in larger quantities and then alliquot them. So in this particular case, if they were all the same type of potion, I'd say fine. Of course, there would have to be some sort of control on quantity consumed.
If game balance is still a concern with larger volume consumption, consider costs. As a GM if you are regulating PC wealth and keeping track of expenditures, larger volumes of potions cost proportionally more. If the PC's spend their money on larger potions, so be it. It means they have used up that limited resource far faster than if they spread it out. In the long run, they will exhaust such resources. Moreover, if you are considering larger creatures consuming larger quantities, make sure to remember supply limitations. A great wyrm consuming a proportionally larger potion of healing would probably tap the resources of the entire region, if that region even made that much potion. You could also argue that each brewer has a slightly different technique and so the only way to get larger volumes is also by the same brewer (otherwise you act as if you were mixing different potions and their effects are ruined).