I think over the past year we have seen a bit of a change in the way that replica watches are made, we have had the chance to see pre production photos and the chance to find the faults and get them rectified before the production models come out. I have read that some of our collectors own a couple of gens that may have been used as plans for reps but i thing as a rule they are made from photos and other information. if every one was made from a gen then we would see many more true 1 to 1 reps, and there aere not that many of them in reality.
When it comes to customising i think the real queston to ask is can someone customise rep A to look like this or that as oposed to the general question you gave. There are many people here that can carry out work for you but the dealers apart from Ruby that has already been mentioned are in many cases just Drop Shippers, they never get to see the watch you get they take the order and pass it on to a shipper who ships it to you, oftern with very little quality control. Do you know what sort of watch you would like and what you would like done with it?