I'm with Shane here, a new design would have to be something very unique and special in order to be worth doing. Otherwise just get an Era or Blackbird, you'll get 2x the edges of a 1/2 blade!
It would be even more challenging to hold a rigid edge on a 1/2 blade, so just get an Era which clamps it like no other. (I am a happy Era owner) AC, GEM, and injectors have a rigid blade which gives a rigid edge. You could make a half-Era using an innovative post like you did with the Vector, but a thinner head doesn't seem like enough of a gain to me. The Era is already slim enough to get under the nose/etc easily.
It would be even more challenging to hold a rigid edge on a 1/2 blade, so just get an Era which clamps it like no other. (I am a happy Era owner) AC, GEM, and injectors have a rigid blade which gives a rigid edge. You could make a half-Era using an innovative post like you did with the Vector, but a thinner head doesn't seem like enough of a gain to me. The Era is already slim enough to get under the nose/etc easily.