"Freezing" per-role settings

Folks,

I noticed a little unimplemented feature which I suspect a lot of
people would find useful, namely the ability to "freeze" certain
settings for a role.

Example: We'd like to create a role called read_only, with eponymous
capability.  At the moment, we can't do what's below, but I'd like to
be able to make it possible.  First, we'd issue the following, which
doesn't work yet:
   ALTER ROLE read_only SET transaction_isolation read_only;

Then, there's one way via DCL (Data Control Language)
   REVOKE SET transaction_isolation FROM read_only;

Another would be via DDL:
   ALTER ROLE read_only FREEZE transaction_isolation;

I'd think of the reverse of each of these as GRANT and ALTER ...  THAW,
respectively.

Is anyone else interested in such a feature?  If so, is it more
DCL-ish, or more DDL-ish?

Cheers,
David.
-- 
David Fetter <david@fetter.org> http://fetter.org/
Phone: +1 415 235 3778  AIM: dfetter666  Yahoo!: dfetter
Skype: davidfetter      XMPP: david.fetter@gmail.com
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