I can't even begin to claim to have the knowledge to comment on the various keeper builds. However, I did want to point one thing out.
Quote 2: You can Stifle his activation on turn 2...
Taken from the CrystalKeep rules database regarding Metalworker:
Quote This is a mana ability. It does not go on the stack and cannot be responded to. [DeLaney 1999/06/08]