I've been googling the subject, hoping for something extra perfect to eliminate from a Wii Remote the very notion of batteries or charging/replacing them. I know how sucky 3rd party battery kits can get, and even Nintendo's expensive one will inevitably lose its charge someday. These doesn't look to be many options that make sense for regular use. Closest so far is this. http://teachwithtech.com/AC-DC-Adapter-and-Wii-Remote-Insert-p15.html
It's not like the Wii mote uses up batteries like a Game Gear. The best way would probably just to use rechargeable AA batteries, because like you said, even the official Nintendo ones will lose their charge and 3rd party battery packs usually suck.
http://www.amazon.co.uk/Twin-charging-remote-Battery-charger-Batteries/dp/B00152D68A Why not something like that?
I've had a charger and it worked well enough. I use my Wii so infrequently that I usually have the batteries out. Now if you could get one of those magnet things that power flashlights by moving it, that might work out.