There are times where the intent is to rapidly shed energy and systems/procedures designed for that (spoilers, speed breaks, slipping the aircraft). I suspect though that implementing any kind of efficient regenerative capability during these times will be something that is developed later/as an afterthought initially. That being said dismissing the idea out of hand is probably wrong. If this system is used during takeoff and climb and would be needed for landing/go around then I imagine they would want minimum energy levels in the batteries so there is probably going to be some system to tap the generator to give them an ability to have minimum energy for landing. Why tap the generator if you can scavenge along the way or just build in robbing power from the prop as the connection to get that power. This system probably naturally beefs up the generator substantially on these aircraft to give them essentially this exact capability. Hmmm.. as I type, the more I think it may happen very quickly honestly. But I'm not an aerospace engineer so this is all a guess!