GTCE has a Credit system, where coins can be exchanged for coins of higher value. 8 lower one to 1 higher one.
Copper -> Cupronickel -> Silver -> Gold -> Platinum -> Osmium -> Naquadah -> Darmstadtium
Instead of using custom Omnicoins for currency, you could switch to the GTCE credits. The only issue you would have to fix is the recipes turning Cupronickel credits into cupronickel dust or fluid. Once those are removed, you could switch the recipes over to the GTCE credits and remove the Omnicoins from the game, saving a few ContentTweaker items.

Cool idea. I am assuming recipes for turning the credits to liquid/dust will be gated in terms of energy tier. This is the only way i can see for balancing since I am not sure of how GTCE credit system exchanges works.

The custom coins have been a feature of this pack from the beginning. We just merged a PR with new custom graphics and a rename for the coins yesterday.

Sorry, but we are not interested in this.