This is a really, really good idea! Hell yeah. Although you're right, implementation will be quite hard :-)
Not sure if the lvl and exp cap is too harsh. On the other hand, the inheritance effect could be really devastating. Hmm, definitely no potion to use on your carry if it drops very late.
An alternative would be, all potions lost, experience kept? Oh yeah, this way keeping potions for later will finally make sense ;-)
Balancing is not my thing :D
I just put in some suggestions how to balance... half all used potion effects or collected exp is also an option (or different numbers)
Thought something had to be reduced for this potion to be balanced
Yes, something like that would be a good first guess. Eventually, I think the only way to find out to give this to the players and see what happens :-)