GnomeBob
Hi author, this is a question that may seem silly but are you going to make a link between the force of star wars and the force of the phoenix of Marvel? I say that because the two have similarities. an immortal, indestructible primary universal life force. She is also the nexus of all psionic energies that have existed, exist and will exist. Maybe I see similarities where there are none.
He finds crystals in HxH that can absorb energy. He applies a crystal to the devil's fruit and absorbs strength from the fruit. There may be failures or stupid effects. My idea of fox fruit from the 6th floor is an impeldown and the result of a chakra beast with a crystal-core. Perhaps as the beast develops intelligence, there will be a chakra armor
Huh, neat. Rather than reincarnation or anything like that I figured Ging made playing a game of tag with his son a Rule in his Hatsu something like his son has to touch him or say 'caught you'. Something he really wants but also something that would dramatically weaken him once it finally happens. So he's going around having as much fun as he still can until that day out of a bit of greediness. I'll admit I'm not up to date at all on HxH though.
To be honest, since you already got the edge covered, then I don't really want the lightsaber to get any devil fruit. They are amazing and the main thing related to the One Piece world, but I don't see any of the options still open being really useful in any way apart from the Dark Fruit acting as a storage for things and energy attacks he receives. The thing with Ging sounds interesting, maybe it could be an arc for the MC to return to the Hunter world after having been to One Piece, to help Ging and Gon on their adventure. Or maybe not.