Why do you insist on limiting the input to 60Hz? Even in the videos Pimax was showing during KS campaign they were having the renderer running at 75 or 80Hz?
The idea of the brainwarp is simply interleaving the images, it does not force any particular refresh rate on the input. The limitations in the current implementation are more related to hardware components (DP chips, scalers, panels, etc.).
In your theory, you limit artificially the input to 60Hz and then come up with an idea how to display this 60Hz content on 180Hz display with complex interleaving and brightness variations which have no benefit.
Do you realize that displaying one frame twice (e.g. GPU_0_L in timeslots T0-T2) will give it two times more perceptible brightness than the following frame GPU_3_L in timeslots T3-T5.
Why would anyone do that, if he could simply display 60Hz content at 60Hz refresh and stress the display much less? (Running the display at 180Hz is definitely more challenging than running it at 60Hz)