There can be problems with making such a mid-stream change.
First of all, a first-time buyer of a SR (for example) is probably going
to want it to sound like the ones he's already heard. Repeat buyers --
ditto for them, unless they're buying specifically for the new preamp.
Phasing over to a differently-voiced preamp would frustrate those
buyers, and might even generate a higher return rate.
Second, a generational change would be created -- for good or for
worse. How to manage that? ..............................................................
.......................................................................................................
................................................................................. etc etc
There're 3 generations of normal SR5's: early alnico, ceramic, later alnico.
There was no problem switching to ceramic. I recall players switching to
the [ceramic] SR5s from their SR4s, saying they didn't really need a 5 but
the 5 just sounded better. For the most part they seemed unaware of any
alnico vs ceramic situation. They just accepted that something mysterious
but real was making the SR5 sound better.
Acoarst it was no mystery for EBMM which led to the ceramic version of
the SR4, christened the "Sterling 4" .... so those who resisted 5-strings,
but had encountered that sonic difference, could buy into "SR5 sound".
What about any players who favored the SR4 sound, but for some reason
they need a 5-string ? Okaaaayyy .... just return the SR5 [ceramic] back
to alnico ... and add a string to the Sterling 4, thus replacing the [ceramic]
SR5 with an identical [ceramic] bass ! And ... edumacate buyers that the
revered and respected but now unavailable ceramic SR5 is still available
but has a new name, called "Sterling 5".
EBMM survived all that and more ... "survived" is waaaay understating it.
They grew. All in all, while all your concerns seem valid taken individually,
your total picture is too pessimistic [and complicated]. Change is normal.
The show goes on !