there are several clustering solutions to choose from, and have been for years.
is your complaint that you know that they exist?
that you think that they would be better if packaged in the same tarball?
that you think that there are too many to choose from?
that you think that they are too inefficiant?
the reason this standby mode is going into postgres itself is that it ties much more intimately to the core code to do it's real-time replication