> 1. Is there any plans to add "non-strict mode" (configurable via options on > server/table/column level) to allow pushing down conditions for all data > types?
No. You might as well call it a "return random answers" mode.
Its bad. I think most users would be happy to have "auto discovery" mode when foreign table fetches all required meta info to act like original table.
Since 9.5 has IMPORT FOREIGN SCHEMA don't you think that foreign tables can be marked as "imported". This 100% guarantees that all user-defined data types/domains (including ENUMs) imported as well. It should be safe to push down conditionals for imported types. Does it makes sense?