Collecting mobile phone batteries with jackets sounds like a good idea, but we already have enough to do in business class before takeoff...collect jackets, hand out newspapers, preflight drinks...and the whole boarding procedure only takes 15 mins.
Also what about economy passengers? They have mobile phones too. Would you like to collect 220 batteries before takeoff and then hand them back at top of descent? On a 1 hour flight this would be impossible.
I find that people often use their mobile phone whilst the aircraft is taxiing. They get really annoyed when they are told to turn it off. I think it is something that the airlines should address, maybe if they charged a frequent flier with engangering the safety of an aircraft he would think twice about doing it again. Unfortunately the more likely scenario is that he would complain that the F/A was rude to him when she told him to turn his phone off. The company would send a letter of apology and something to compensate him.....