Good points. There is no way of letting others know whether you do or don't have enough battery to use the res unless the add some visual effect to the MCH but I don't think players want to see their character glowing or something everytime they have enough battery. Plus there are players who turn off all visual effects.

I still like it and think it would be an interesting battery alternative. Plus why should casters, besides BLM, be the only ones that can res.