Aren't there two aspects to this which people are confusing? One is corporate personhood in the sense of corporations being treated as single entities capable of entering into legal relationships separate from the relationships of the shareholders, board, etc. The other is corporations being granted (some of) the civil rights of real people.
So the point of abolishing corporate personhood isn't to replace corporations with some other legal form - it's to remove some of the restrictions on regulating corporations which the current interpretation of legal personhood forbids. The regulation Nathan is talking about doesn't seem like it would require massive political reform, and it's certainly not some kind of quasi-socialism. Abolishing the legal personality of corporations might be, although if it were, presumably John Q Moneybags would just stop using the corporate form.
(I seem to remember reading in a Micheal Moore book about some piece of civil rights law under which only twenty cases, or something, had been brought by actual people, with the other thousand uses being corporations, but I can't remember the details) --
"There are very few members of the establishment press
who will defend the idea that things like aggressive
flatulence, forced feedings of swill, or even a barely-
muted hostility on the part of the candidate would
justify any kind of drastic retaliation by a professional
journalist - and certainly nothing so drastic as to
cause the Democratic front-runner to cut short a major
speech because some dangerous freak was clawing at his
legs and screaming for more gin."
-- Hunter S. Thompson Tim http://www.huh.34sp.com/