yeah usually when it comes to designer lines, theyre very flexibble when it comes to which stones you want, what karat gold or plat, etc. if your jeweler is in contact with a rep like you said, there should never be a problem with customizing a little.
we just opened accounts with some nice designers like Daniel K (
www.danielk.net ) and this indian guy whose company is named Vibhor (he has machines that make better work then Tiffanys for half the price)