Interesting, but you must not have been looking very hard back then. ETA-powered Rolex reps were coming on the market in the late 80s. In fact, I did my 1st franken in the late 80s. Still keeping reasonable time today (with genuinely-aged tritium lume)
Ubi - The best Pateks are those that, @ 1st glance, look completely innocuous & generic/utilitarian, but prompt an almost autonomic 2nd-look.
Ending the work week wearing my CHS
The 6542 was powered by a 10xx movement. The 1675 was powered by a 15xx movement. In addition to the date windows being located ~.5mm differently, the 6542 dial is pressed onto the pillar plate & the 1675 dial uses standard dial feet, so they are not interchangeable.
If Rolex did service a 1675, they would almost certainly require the perspex insert & bezel to be changed to modern replacements. However, because the movements are different, a 6542 dial will not fit the 1675 (which is the type of dial in accio's watch). The hour/minute/seconds hands are interchangeable, but I am not sure about the 24-hour (gmt) hands?
If, by profit, you mean selling a franken-gen as a franken constructed from gen parts, I see nothing wrong with that. But I would not try to sell it as a standard (assembled at the Rolex factory) gen.
Absolutely (yes), if you are building an all-gen watch (or, possibly, all gen except for the mid-case & you have an exceptionally accurate aftermarket mid-case) & you are missing is the dial. Otherwise, probably not.
Very nice dial.
I have not found a source for consistently good aftermarket hands. All appear to be luck-of-the-draw. My best & worst handsets came from DW (listed as same part).
For reference, a low amplitude means that gravity & acceleration will have more of an effect on timing. In simple words, timing variations are likely to occur day-to-day.
I agree with the previous recommendations. You need to remove the balance & inspect it carefully. If the watch is running fast, most likely the hairspring is crimped or tangled on an adjacent wheel or bridge. Also, check to be sure the cap jewels (both upper & lower) have reset to their center/null positions in the shock assemblies.