This astonishing reanalysis was just suggested by Wes Munsil, who “wonders what mental model this usage reflects”. Indeed. It’s not even that rare.
ADDENDUM, following orionrobots’ question in the comments.
The eggcorn is puzzling: Most of our collection involve not more than a misunderstood lexical item, or maybe change morphemes or function words. This one, though, takes a rare but perfectly normal transitive verb and creates a) a predicative structure “(it would) be X”; b) an indirect question “who of (you, them, us …)”, which takes the place of the predicative complement X; c) the preposition “of”, which takes what would have been the complement of “behoove” as an argument. The result is grammatical. “Who of me” doesn’t seem to make much sense, but I’ll come to that later.
There are of course irrelevant (non-eggcorn) examples of this:
* We are waging a presidential election in this country at this very moment, the major issue of which seems to be who of these two men is the greatest warrior? (link)
For “would be who of”, the eggcorn takes over, but some examples are still perfectly commonplace:
* An interesting one would be who of our players has consistently failed against the Kangaroos (under Pagan). (link)
Here’s an example I didn’t include — I think it is the eggcorn, but maybe the passage shows how it might have arisen: imagine the question being asked provocatively: “Who of you would consider it?! Well, you should.”
* I have compassion for the plight of those who’re suffering in the hell hole that is New Orleans. But I have very little sympathy. From this time forward, when you’re advised about a “mandatory evacuation,†it would be who of you to consider it, especially if you want any moral consideration of your “Monday Morning Quarterbacking†after the emergency.(link)
For “it would be who of me to [do something]” to make sense, the new structure must have crystallized into an idiom for some speakers. I nearly wrote that it would be unlikely to find eggcornified “it behooves you”, but digging a little further…
* The doctor doesn’t know the Mafia’s choice, so it is who of him/her to protect valuable townspeople and hope the others do not get shot. If somebody asks and you are the doctor, you MUST say so.(Google cache link, from the description of a role playing game)
* This is also why I try to stay current on what the afroementioned nine wise in Washington do. Their case law changes all the time, and it is who of us to keep abreast. That is good civics. (link)