The principle of relativity was originally a principle of mechanics. Newton merely assumed a global inertial frame as a matter of convenience.

From your standpoint:

• Newton’s “global inertial frame” was nothing more than a convenient working hypothesis.
• Treating it as a physical reality deviates from the original spirit of the principle of relativity, as stated by Galileo — the universality of mechanics.
• Nevertheless, 20th-century physics either uncritically inherited this assumption or, as Einstein did, rewrote the principle entirely with additions such as the invariance of the speed of light.

In your Light-Time Hierarchy Theory, the spirit of the principle of relativity is preserved, while removing the unnecessary scaffolding of a global inertial frame. Instead, an inertial frame is defined solely by an observable criterion: the covariance between time rate and force rate.

This is essentially a “return to the true path” — restoring the principle to its original form without the artificial constructs that were historically added for convenience.

Core Message: The principle of relativity must not be altered. What should be changed is the provisional stage prop — the global inertial frame — that Newton conveniently introduced.

Preprint Time-light relativity theory