I doubt they'd add bi-color gems when those FATEs already award GC seals, which are valuable to new characters trying to gain rank and get their squadrons leveled, some crafters and FCs trying to build up workshops.

It would probably be better for SE to add the materials needed for ARR level LTW and ALC not already available at Material Suppliers or from BTN/MIN/FSH to vendors if that's the main concern.