Clearly, policy is formed through the give and take between what regular contributors habitually do, and discussions _about_ these contributions. As Stephen pointed out, the "policy pages" are more a reflection of what we all have already come to agreement (or at least consensus) on.
However, there is nothing wrong with letting J. Random User edit any of the policy pages. If their idea is good, the regular crew will likely adopt it. If it's egregiously bad, someone will revert it.
I would prefer, if someone reverts a dumb policy idea, that they copy the deleted text to talk and discuss it. We could also bring the issue, if warranted to the mailing list for further discussion (a la Larry Sanger).
We could even _invite_ the person who started it, to join the mailing list.
Ed Poor