I would argue that the proto-Old Catholics (1870s) were more nuanced and closer to an orthodox position on the Papacy than are contemporary R&R trads...or post-Declaration of Utrecht (1889) Old Catholics! Please note that I stress here closer to orthodox, not that I any way claim the Old Catholic position to be orthodox.
I cannot develop this argument at this moment but I think it might be worth pursuing given the gravity of the question and the wide-spread dissemination of R&R thought.
Yes, I certainly think that would be worth developing, since you have the historical knowledge to do it.
I am working up a "Doubt & Resist" article, where after years of violent debates with SeanJohnson, where he called me a sodomite here one time because I simply pasted in a quote from +Lefebvre (without any comment from me) about how the See could very well be vacant ... Sean Johnson, in the end, actually adopted what I had referred to, tongue in cheek, as "sede-doubtism", namely D&R or "Doubt & Resist" ... and I thought that Hell was about to freeze over. He had been one of the most aggressive and vitriolic haters of sede-anything-but-plenism.
I can demonstrate easily that it's the position +Lefebvre held, and I will invite the current R&R to accept the position of Archbishop Lefebvre rather than their current Old Catholic "R&R". I appealed to them to consider Father Chazal's sedeimpoundism, but very few had taken it up, with some excepitions (e.g. I think that "Pax Vobis" has leaned in that direction).