Additional currency types is 100% bad design

Instead of adding greater this, perfect that... simply attach the tiers of rolls that can happen to Item Level in a scale of your choosing.

All rolls can occur, bad rolls are just less likely to happen on an i84 base compared to an i60 base for example.

We don't need more basic currency types to create the higher probability, simply higher base level items.

One additional currency you could add though... Scours...