Perhaps the cradle would be better unless you ever have 6 hours plus gaming sessions.
I don't often have 6 hours+ gaming sessions but it would be nice to have a decent battery in the controller, especially if I can get one cheapish.
http://www.product-reviews.net/2014/01/16/ps4-secret-with-double-dualshock4-battery/What size batteries are you looking for the controllers? I have a friend who is a wholesaler, he can get odd shapes and sizes if required.
It's the same as the one in the above link.
Don't see the point personally myself.
Do you have a wall socket/USB near where you sit? Plug any android phone charger into said socket and then into the controller = never run out of battery again.
What would be the point of having a wireless controller then?