They really should have never added quick synthesis, and just have gone with my suggestion from way back when....

Stay in synthesis modes until you run out of materials, or press quit. That is all. Once you finish a synth, if you have materials to make more it just restarts the synthesis process, full CP, full durability, 0 progress and quality matching what materials were used and items re-used.

I should point out that they already have it so that your materials don't really get used until you perform an action while in synthesis mode. If you select synthesize, but press quit before doing anything, you don't lose any materials.