I own the all gold blue dial that you have pictured, have had it about a year now. I don't wear it everyday by any means, but I've worn it enough to know that wear through in the plating isn't a problem, at least not in the near term. I think the stories of wear through harken to the days of really bad replicas. Mine appears to be about the quality that Joshua sells. In fact, I think the guy I bought it from buys from Joshua meaning I probably paid about $100 too much. It's a heavy watch, looks impressive on the wrist and mine keeps dead on time, +/- 5 seconds or so a day or actual chronometer standards.
What is a problem for any gold filled or gold plated watch is a propensity to tarnish. This is true not only of reps, but also genuine gold filled and gold plated watches. In addition to my interest in reps, I'm also a vintage gen collector. I can tell you that I've never seen a solid gold watch that was prone to tarnishing and never owned a gold filled or gold plated that didn't tarnish, at least to some degree. I'm not an expert, but I would guess that the problem relates to a reaction between the gold and the base medal.
The solution for tarnish is to polish, polish, polish. Connoissers makes an excellent polishing cloth that can do the trick. The white side is for cleaning, the pink side for polishing. Realize that tarnish on a supposed $20,000+ watch is a dead give away. There is no way that a genuine Rolex would tarnish. (The way that you can spot the tarnish is that unfornuately, it nevers seems to tarnish evenly). The down side to keeping it polished is that it always looks virtually new. You'll have to come up with your own story to tell on that front. I usually just reply that I'm a dweeb who sits in front of the tv polishing my watches.