This would be great Omega, but how do you handle partial cells? its common practice to reload a partially empty gun so you don't have to do it during combat. If you think of the cells like magazines and you simply have the ability to magically divide them into there components. Just ignore the handwaving of being able to divide a cell up like a magazine and things make more sense.
Cells with, for example, half energy would be at that, half energy, even if you change weapons. It makes sense, but you would have to switch between cells manually. You could just press square or whatever to change the cell out for another one, and it should even be that you are switching to the one that has the most energy in your inventory. It wouldn't be like it is now, with all the ammo being combined into one giant mass of ammo that all magically fill into fill cartridges, but each cartridge would be separate from another one.
so you would have many MFC's in your inventory, some that say MFC (240), MFC (60), MFC (120) etc. They would all be unique depending on the energy amount in them. Cells with the same amounts of energy would be stacked on top of each other tho, like MFC (240) x5, to reduce clutter.
This is also where combining used cells to fill them up comes in handy, to fill used cells to full energy