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There's a well defined notion of a static observer in a static space-time like the Scwarzschild space-time and there is an unambiguous notion of the speed of any object relative to the static observer that's co-located with him.
Cosmological space-times are for the most part not static, so this trick won't work for them.
Cosmological space-times are for the most part not static, so this trick won't work for them.