Re: POST vs. separate methods
The issue is change control: once you define the semantics of a new
method, there's little or no way to change it or update it. Adding new
methods is currently (intentionally) difficult. PEP might make it
easier, but I'll believe in PEP when I see more progress on it.
On the other hand, there's a well defined mechanism for defining,
modifying, agreeing on, registering new media types.
So "POST with new media type" isn't equivalent to "new method" in the
important dimension of "what happens if we get it wrong".