I don't think putting them in energy slot would be a good idea, because then it soils the opportunity to use energy weapons that would pair well with them. The only power weapons you'd have then are long range weapons, save for grenade launchers. Increasing their base and total magazine size, in addition to reducing ammo costs for power attacks and guarding, could work out fine. Making guarding more responsive following a swing would also be very nice. The Crown-Splitter, and future aggressive-frame swords, could really do much better if they didn't have a lunge attack. Lunging often hurts more than it helps, latching onto a single target rather than allowing one to take advantage of its cleave effect(given that enemies very often try and skirt around the player when they get close, especially melee enemies like thralls.) It makes its power attack especially useless. Speaking of frames, it would be nice if crown-splitter and quickfang weren't the only aggressive and lightweight swords in the game. Every single sword except these two has the same adaptive frame moveset.