psql commandline conninfo

I have been working on providing psql with the ability to accept a libpq
conninfo string, so that the following now works for me:

psql "conn:service=sname user=uname"

Instead of providing yet another switch, I overloaded the dbname
parameter so that if it has the recognised prefix the remainder is
treated as a conninfo string. I have 3 questions:

1. Is this a good way to go, or should we just provide yet another switch?
2. If this is ok, what should the prefix be? is "conn:" ok?
3. Should we append settings from other switches to the conninfo (e.g.
-U or -h), or should we just ignore them? If we ignore them should we
warn about that if they are present?

cheers

andrew