Avoid full page images in streaming replication?

ISTM it should be possible to avoid sending full page writes to a 
streaming replica once the replica has reached a consistent state. I 
assume that the replica would still need to write full pages to it's 
disk in case of a crash, but the sender could insert special WAL records 
to tell it when to do so, instead of sending the full page image. 
Presumably this would be a big win for replication over a WAN.

Am I missing something? I see that pglesslog is no longer supported but 
couldn't find any particular reason for that...
-- 
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com