#2
i don't think that would work well, doesn't epoxy have a rubbery texture? also wouldn't regular play wear down the epoxy (especially bending strings across the fretboard)?
#3
epoxy is usually used to glue inlays in place--not as the inlay itself. epoxy is usually a mixture of solvent and catalyst, which then hardens. you could try making a sheet of epoxy and cutting your inlay out of it, but epoxy is fairly hard. you're probably better off sticking with abalone or abaLam--try stewmac or lmii
#4
well there are epoxies and there are resins. epoxies are more commonly used as glues for inlays but if your looking to submerge objects in a routed out area resin is the way to go
#5
I've seen inlays made out of thinner plexiglass, you can place an image or somethign under it