Yes, however one cannot demonstrate that the devices called “accelerometer”and “gyroscope” actually measure “accelerations” and “changes in orientation” without invoking somehow the laws of physics. Such devices can provide a more accurate assessment of our state of motion than our senses, once it has been demonstrated that they are fit to purpose, but beforehand the need remains for an independent definition of “inertial” (see below). I agree with many of your statements which I find better than mine, in particular the need to refer to a consensus between observers. However I think a more logic presentation can be proposed if the postulates leading to SR are set at a deeper level, as follows. This is not derived from your assumptions, it is a postulate, the first postulate from which everything will flow: my sensation reveals an objective property, a qualification upon which all observers will agree. Then, assuming I do not sense any acceleration or rotation in my body, my state of motion can be defined as “inertial”. Hence a 4-coordinate system attached to my body and reflecting my time flow provides an inertial frame of reference. I think this definition is immune from contradictions whilst removing the indirect reference to laws of physics (via "accelerometers"). A second postulate is required in order to derive the Lorentz transformation (assuming no further constraint will reduce the generality of the development alongside Rindler's approach), whereby the difference between representing oneself at rest or in constant motion is non-objective, conventional. Thanks to the first postulate, the equivalence relationship “to be in constant relative motion” structures the family of all possible frames of reference in such a way that the associated transformation will map an inertial frame onto an inertial frame. Thanks to the arbitrariness set by the second postulate, one may conclude that: In conclusion two independent postulates are required for developing SR, which are of a more general nature that those often proposed.