Make Nitrogen easier to acquire (It is 78% of the atmosphere of an earth-like planet is Nitrogen after all...).
I'd leave the IC2 'compressed air cell' alone, but make it need to be split into N2 and O2 in a 4:1 ratio to be useful as elemental Nitrogen or Oxygen... necessitates adding new O2 and N2 cells and adjusting recipes to match obviously.