i meant like 40 exp or 20 seec to 40% + exp gain over 40 seconds
That could be done, but it would lead to occasional 'eternal states' that never go away, even when you save and reload the game, and states that cancel each other out instead of stacking or replacing, potions not working and all that interesting stuff. I believe you can even stack antidote and thawing potions in classic LoD, but neither has competition from other potion states, while there are few states in Median that do not conflict with other states.

Oh and regarding my first post, no need to be sarcastic dude.
There is always need for more sarcasm.