So, suppose there's a bar on the HUD for stored enchantment charges. Replace the scripts for soul gems so they fill this bar. Detect when the player is using a charge attack or pulls a bow all the way back, and if the weapon's charges are insufficient for one attack and there is enough charge in the bar, transfer that amount to the weapon.
Would this work? Is it possible to reliably detect when the player begins a power charge and perform an action only once for that attack? Will the weapon enchantment work if there's enough charge at the end of the attack animation but not before?
Thanks