Potion/Revive Trade In
How about a system where you can trade in your lower rank potions and revives for the next rank up. Maybe 5 of rank 1 can get you one of rank 2 and so on.
It will still be much faster to use credits/glory/loyalty to obtain the higher rank potions/revives. But it does provide an option for those wanting to play the long game or for those who don't want to sell all the excess in their cache.