As Ci user to be it is water resitant any way.
I will be using batteries (for many reasons) also i think rechargeables aren't much environmental friendly (or cheap) cos u'll need to use electricity (however small) to charge them up for hours, have short life expactancy (Ci Centre told me it's one year before it starts to wear out, then you buy new set) It's little bit of pain carrying everything with you when you go away with work (i am known to forget my hearing aids batteries!!) the cost of replacing new rechargeable batteries is higher than getting box of one year's supply of batteries.
What i would like is a choice of a powerful hand generated rechargeable batteries like small hand wind up and small enough you can put in your pocket/purse just in case you are stuck without spares. That would be my wish cos as a crew on racing yachts which we are often in middle of no where... We cant use weight, or use batteries to charge them up, also that it is environmentally friendly cos no electrcity is used.