Realistically, to me, shields should be regenerating whenever they're not taking fire. I think there needs to be special a reason why it is called 'regenerative' shielding.
That said, I like the idea that regenerative shields somehow absorb incoming energy for use. I don't like this as being redistributable to other systems, though.
The way shields were depicted in 'Equinox' might be worth studying, or might only complicate things. I seem to remember the crew somehow managing to reinforce keep the shields up even after the generator was stolen, using the nav deflector? Perhaps then regenerative shields tie the nav deflector into the shield system to absorb the energy expended against them.