Currently, I don't think there'd be much use for them; mostly because currently reactors are tiny. Even a warship armed with large numbers of rapid fire beam weapons is only going to need a tiny portion of its tonnage be devoted to reactors.
Now, double the size of reactors (with a corresponding reduction in the size of energy weapons), and add in capacitor banks, and I think you'd have something. In fact, IIRC Newtonian Aurora uses such a system, maybe it'll eventually get brought to standard Aurora like the engine changes were.
It would also add interesting design possibilities, like an overgunned warship that could fire it's light point defense weapons, or its heavy anti-ship weapons, but not both at the same time, mounting more of both since it saved space on reactors.