the idea of 3po not appearing til ROTS doesn't bug me, but how will you be able to pull that off with all the scenes he's appeared in?

When I first heard Anakin built (actually rebuilt) C-3PO I cringed because it seemed contrived, but that was only because I saw the OT first, if I had seen Episode 1 first it would not seem so small and contrived, it works if you watch them from 1-6 for the first time. It's also symbolic of what Anakin largely becomes. The droids are Anakin and Padme's and they are left with the Organas and Captain Antilles at the end of EP3. Why is that so bad, or hard for some people?

Owen not recognizing 3PO is a no-brainer, it's 22 years since he's seen him, C3PO is gold plated, a common looking droid and not the grungy thing he was 22 years prior. Owen seems to regard droids as only appliances anyway, and never even is told 3PO's name by the time he dies a day or two later in ANH.