Lemurian
I find the most telling sentence in your explanation to be :
It is to be remarked that this ceiling would be attained at only one Mach number.
Would it be correct to say that at a higher Mach number one would for the same mass and altitude require a lower Cl to maintain 1 g flight and therfore the limiting factor is in fact thrust?
With more thrust at the same altitude a higher Mach number could be obtained and thus a lower Cl.
Could recovery from this ceiling not be safely be obtained by lowering the nose and making an accelerating descent. As in doing so Cl is reduced and therefore high speed margin increased?