I am wondering if the keel reinforcing piece with all the epoxy that fills the void between the v of the hull and the flat piece is really needed or a matter of super overbuilding.

It all depends on how rough you're going to be with your pride and joy.I am constantly amazed by how tough a 3-4 mm lamination of glass,wood,glass is but that rock embedded in the sand just waiting for your keel to land on is why you are adding structure but also weight..your call as to if it's needed or not.I do know that light weight is golden.I often choose my lightest boat over the most practical.
cheers,