There’s no facility to add OPTIONS to an EXTENSION right now, so this capability seems to be very much server-by-server (adding a FDW-specific capability to the EXTENSION mechanism seems like overkill for a niche feature addition).
Options already exist on CREATE FOREIGN DATA WRAPPER, so it should be easy to support that.
I'd rather add it once on the wrapper than be forced to list all the options on every foreign server, unless required to do so.
--
Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services