I have to disagree with your interpretation of events and of the lore.
-- Hal and Guy were the only two equally worthy at the time of Abin Sur's crash. And yes, I think at the time,(before the Guy retcon) Hal was meant to be "singularly worthy" - the best of humanity. Hal was selected for being closer than Guy, but that's it. Guy was then the backup, because he was the only other one worthy at the time. John wasn't "third closest" - being too young was their way of not saying he was less than Hal and Guy.
-- John was chosen as Hal's backup because Guy was in a coma and out of commission. So that's what I mean by he was pre-selected. That's not a retcon, that's how he was introduced. He was third most worthy (or equally worthy) I suppose, but anyone on earth worthy enough could have been chosen to be Hal's backup at that time - it wasn't an emergency and proximity had nothing to do with it.
As for the rest of it, it then depends. We are shown that backups were chosen ahead of time (which has nothing to do with proximity) although the comics have been inconsistent about this kind of thing, especially when they show the rings go in search for a worthy replacement when a GL dies instead of flying off to the pre-selected replacement. That's not a concept that was done a lot after Guy and John were introduced. It also depends on how rare you think it is to find a "worthy" replacement. It was seen to be much rarer originally, but I think people don't like the idea that there are only one or two on earth worthy - as the glut of current GLs has shown.