schema level variables and deferrable unique constraints

hi!
I apologize for mailing on the hackers list but I posted on the general
list and did not get a good answer.
I have two independent issues, but am addressing them together.

1.
Oracle has package level variables which are not mappable to any postgres
equivalent.
could we have something like schema scope variables which could be
directly referred from let's say plpgsql functions?
Can someone give me some pointers on how to go about imlpementing this?

.
Postgres does not support deferrable unique constraints.
we would however like to support this especially as some updates give
non-standard behavior because of this.
for details please refer to