[OpenID] Negotiating a backup OP from the current OP

I was reading this:
http://self-issued.info/?p=75
(Posted to the board <at> openid.net list by Mike Jones.)

I was disturbed to see, in the first paragraph, that OpenID would be 
accepted from "two" Providers; this is exactly the kind of lock-in 
that will effectively *lock-OUT* the small, independent Providers.

Listing multiple OP's on the claimed Identity page may be one way to 
get around that; just let the RP discard options until it runs out of 
OP's or finds one it likes. But why should each user have to handle 
their own complexities this way?

Couldn't an OP offer that sort of thing as a feature? Couldn't a RP 
trust an OP designated by the user to at least report which *other* 
OP's the user had approved for use if the RP didn't trust that OP to 
authenticate the user?

I don't know what the flow would look like here, but I'm thinking 
vaguely of something like the RP sending the user to the listed OP 
with some arguments like "openid.untrusted", and possibly an 
additional value for the preferred OP, or maybe the OP would respond 
with an affirmative if it wanted to open negotiations with the RP 
about what OP would be trusted. At some point the user would then be 
sent to their OP, get prompted (or at least notified) about accepting 
the other OP (or given a list of their options, whatever the RP would 
accept), and proceed on to the new OP using the arguments that the RP 
sent to their OP.

-Shade