DozyWannabe,
You wrote:
"Obviously, being a relatively new technology as far as aviation use is concerned, some of these requirements will probably need to be tightened as more real-world use cases highlight potential issues."
You are so right - I would even omit "probably"!
You then say that other battery technologies cannot supply enough juice required for the systems.
This is not quite correct.
An example:
On the A340 we had 2 main batteries (NiCd as far as I remember) each with 37 Ah - makes a total of 74 Ah. The Boeing 787 has 1 main battery with 65 Ah.
We had an APU battery with 37 Ah - the BOEING 787 uses the same APU battery as the main battery, i.e. 65 Ah - quite a big battery just for APU starting and a few lights.
So enough power with the "old" battery tecnology, but with penalties in space and weight - double up I guess.