Mithrandylan, yes it was directed at you, but also at Ambrose, as your two views are quite similar.
Okay, a few quick points.
1. Your idea makes the teaching almost impossible to apply, whereas both Cardinal Billot and Fr. Hunter imply it is a quick and easy rule. Take the case of the former, Savonarola had various grievances with Pope Alexander VI, and he also accused "with all certitude" him of various things, of simony, of heresy, of not being a Christian and not even believing in God. Shouldn't this prove definitively that Pope Alexander VI was not Pope?
Not at all, says Cardinal Billot, it is not even necessary to examine the specific facts of the case, the very verified fact of universal acceptance of Pope Alexander VI at this time, proves that he was Pope. Now, according to your reasoning, Savonarola could have replied to your objection, "Ah, but nobody is really following Pope Alexander VI, as they don't imitate and put into practice the same things he is doing". But obviously Cardinal Billot regards that as false, he regards it as easily verified that the Pope had universal acceptance, and that this fact takes precedence over any accusation and infallibly proves that Pope Alexander VI was and remained legitimate Pontiff.
2. If the una cuм is not a sufficient manifestation of the profession of communion with the Pope, please give us the simple and easily verifiable measure, manifested in the external forum, recognizable by the simple faithful (as the authorities cited presume exists, in the case of Pope Alexander VI et al) that is.
3. You're ignoring the difficulty this causes to your position, which Fr. Hunter explains wonderfully. If you insist Pope Francis is outside the Church, and if by all appearances the whole ecclesia docens professes communion with him, it would follow that the whole Church teaching is outside the Church, which is absurd. Therefore, the truth is that Pope Francis is inside the Church, and is the valid Pope. You need to find and show us, for the argument to have some plausibility, these bishops with ordinary jurisdiction that denies Pope Francis' pontificate, and in a sufficient number as to undercut moral unanimity of the recognition.