i think those conglomerate HQ may set some "Strategic directions" to Brands under their portfolio eg.
pricing, marketing, after sales service/availability of parts, uses of proprietary movements/parts/
straps/etc, designs style...
is interesting to read G.MAC view on the resale... sometimes i also have the same feeling... hope
you can share some of the brands/models that have resale value ... as far as i know only
Rolex (sub, daytona, GMT2) and basic panerai models "depreciate" less.... i am keen to find
out more too

There actually many independent watch makers... probably their profit margins not set to high due to
limited marketing/advertising/less celebrity endorsement/sponsorship..
Independents i bought before is the Fortis, Ball, Solvil Titus.. quite reasonably priced..quality on par
with conglomerate.
Other indepedent companies i can think of including Maurice Lacroix, Frederique Constant, Raymond Weil,
Breitling, Longines (not sure), Certina, Vulcain, Oris, Sinn, Stowa, Poljot, Laco, Azimuth, etc and the high end such as HYT, Speake Marin,
Urwerks, M&BF, BRM, etc..