This is known problem, that's why we stop developing jsquery and are working on sql-level query language for jsonb, then you'll use all power and extendability of SQL. The idea is to use power of subselects and unnest to unroll jsonb to sql level.
This is very interesting. Thanks for the update. And to all who answered this topic, sorry for awoling. I just got busy, but thanks for all the replies, I got something to think about.
But I'm afraid it'll come to 9.6.
I'll hope it comes in 9.6. I'll definitely look forward to that.