While I understand the motivations behind this proposal and actually support them, my concern is that the word 'objective' can itself (in this particular context) be subjective. I'd argue that it's possible (albeit unlikely) that this proposal, if implemented, could muddy the already murky POB waters. At best, it's likely to reduce magical traffic and I'll deal with that assertion first.
The proposal above actually does fit into our existing zeitgeist of POB definitions but my problem is that using the words objective and magical crosses the streams, so to speak. Either your system of magic is so well defined that the question involves no speculation whatsoever and you could extrapolate out the answer for yourself (but it's objective) or the question seeks a technical solution to a seemingly magical effect in keeping with the kinds of questions we like (but contains some measure of opinion on the 'best' approach).
When you get right down to it, the reason that POB gives us so much trouble is that it's a continuum - We know what blatant POB looks like, we know what blatant objective questions look like, but we're not really sure where one becomes the other; it's a boundary condition problem. Add to that the fact that we all have a slightly different perspective on where the boundary actually is, and we discover that the question of where POB starts should probably be closed as POB.
@JBH, I think that your constant efforts to help us define this are exemplary and worthy of the best contributors to this august site. It's clear that your passion to resolve this exceeds the patience most of us would have with dealing with this problem. That said, I'm wondering if in fact we (as a community) are approaching this problem from the wrong end.
Instead of trying to tie down as precisely as possible where the dial for POB should be set, perhaps it would be better for our serial VTC'ers on POB to show a touch more restraint.
I do not say this as a criticism; I know many of you are as passionate about this issue as is JBH. I say it more to point out that if you have the option to VTC and you have any doubt about whether or not to do so, perhaps you - well, shouldn't. In so doing, you leave the question for those who believe it's legitimate and want to provide an answer. If you're certain the question is POB, then close by all means, but this would allow people to set their own dials a little, and make their own judgement calls.
Alternatively, if you feel that aforementioned doubt, hold off on the VTC for 24hrs. We tell OPs not to accept an answer before 24hrs so that the entire globe gets a bite of the cherry, so to speak. Why not do the same (on a voluntary basis of course) if you're not sure about a question's POBness?
(I'm not recommending a 24hr waiting period on VTCs because I know that would cause more trouble than it's worth. All I'm saying is that a bit of latitude on doubtful calls might at least allow a VTCer to judge based on the relative merits of the answers as much as the relative merits of the question.)
This approach would at least afford those who fall on the side of it being a legitimate question posting an answer and potentially getting it accepted. It might also give VTCers some context (in terms of possible answers) before making a final decision. It would also (in theory) allow site contributors to make up their own mind on where the dial should be set and answer questions before they get closed if they feel they have an answer that is objective, even if the question isn't.
To quote a famous fictional union rep, what we seem to be asking for is clearly defined boundaries of uncertainty and doubt. Perhaps (with respect,) we need less effort in policing this issue, not more effort in defining it.