Seiko itself acknowledge that its GS brand is not well known enough, and therefore it is addressing it via new investments and expanding distribution. Historically, its watch making capacity (a combination of automated part production, machine finishing, hand finishing, movement adjustment) can only fulfill demand in the Japanese market. It was only in 2010 that GS was made available internationally after Seiko made the necessary upgrade in production capacity.
AFAIK, there is no plan by Seiko to consolidate its high end products under a new brand umbrella, as in Lexus, Infinity and Acura for Toyota, Nissan and Honda respectively. In fact, Grand Seiko, Galante and Credor are already sub brands positioned in that segment. Seiko knows that its premium brands appeal and are already known to watch connoisseurs - maybe it is fine with the status quo. It it worth noting that the size of Seiko's watch business is small relative to its printer business under Seiko Epson. And that revenue from selling premium watches will always pale in comparison with selling affordable (but value for money) watches. Maybe, its priority is different compared with the car manufacturers who wish to directly challenge the likes of Mercedes, BMW and Audi.
I think Seiko has a long term plan to make GS a well known brand for its high quality (and sparkling) finishing, its movement accuracy and its reliability, as all GS owners will know - just that it is not doing it in a big hurry for the abovementioned reasons.
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If you google enough, you will find that its either an undiscovered, undervalued gem to some but to the majority, it is just a ridiculously over-priced Seiko. That is a choice only you can make.
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To be fair, Seiko has not put in the same effort to blanket advertise the GS line in the mainstream international media outside of Japan (and maybe Korea and Taiwan), so most people on seeing one would just assume it's "just a Seiko." It's a brand awareness thing.

In fact, if and when Seiko decides to go wholly international with it and challenge the top Swiss luxury watch brands, I would think Seiko should spin off the Seiko GS line into a separate name like how Toyota "spun off" the Lexus line (while still owning it) to avoid the Toyota name and challenge the likes of BMW/Audi/Mercedes.

Incorporate all the top end line into a single Credor name?

totally agreed! 