1 machine + master DB with postgres_fdw + multiple DB instances on different ports

Does anybody have a similar setup:

[a] 1 physical machine with half a terabyte of RAM, Xeon E7- 8837  @ 2.67GHz, huge ZFS pools + ZIL + L2ARC
[b] master DB pg9.3 postgres_fdw with read/write capabilities, with tablespaces and WAL on separate zpools, archiving enabled (for zfs snapshots purposes), +17K tables, multi-TB in size and growing
[c] multiple DB instances listening on different ports or sockets on the same machine with [b] (looking at 2 DB instances as of now which may increase later on)

On the master DB there are several schemas with foreign tables located on any of the [c] DB instance. postgres_fdw foreign server definitions and all table sequence are on the master DB. Basically, I'm looking at any benefits in terms of decreasing the master DB scaling, size, separate shared_buffers and separate writer processes per instance (to utilize more CPU?). I'm also planning on relocating seldom accessed tables on [c] DBs. Am I on the right path on utilizing foreign data wrappers this way?