Even Telefunken North America's representatives would probably agree that nothing matches the emotional draw, its musicality, and focus - summarized at "three dimensionality" - of an original U47/48.
What components are responsible for that quality in the original, that are missing in copy mics?
Principally, there are three (capsule, tube, transformer) and many more small factors that fill the gaps in between the big three.
As none of these components are present in the copy mics, none can deliver what a genuine U47/48 can deliver. Yes, you may get as much as one third closer to the sound of a real U47/48 by installing one of the original components- a Neumann K47/48, but don't kid yourself into thinking that this Frankenstein will deliver the sex appeal of a well-working original Neumann microphone.
One should also add resale value into these considerations. Used copy mics usually depreciate quite rapidly and severely in value, compared to originals, which have appreciated continuously ever since the mid 1980s, when the buying public finally got over its initial love affair with all things transistorized.
In sum, putting original, pricy, components into copy mics is a mixed bag, with marginal sonic improvements and no change in the direction the value of copy mics takes: down.