PM @ARKM, he knows as much about FX as anyone here I would say. If you can make your sabers fit with some of the standard blade holders from Vader's Vault, CSS or The Graflex Shop you're home free.
While there are others here that know a lot more than I when it comes to making sabers and installing electronics in them, I've made and installed enough sabers to know what is needed to make a hilt FX friendly. A basic hilt consists of three main parts... the handle, the blade holder/emitter and the pommel. 1" diameter blades are still the standard and several manufacturers make 1" dia. LED/heat sink modules. As such, your best bet is to make the blade holder bore at 1" in dia.. The LED/Heatsink module can be inside the blade socket and can be easily secured via a set screw that pins up against it, the same way the blade retention screw secures the blade inside the blade socket. As for the inner diameter of the handle, 1.25" is your safest bet and is commonly used. For the pommel, the easiest way to vent sound is through the bottom but some, like myself, have done side sound venting. I hope that helps.