Heya,
Just pushed support for more settings that are allowed to be dynamically updated on a running cluster / indices: https://github.com/elasticsearch/elasticsearch/issues/758.
The above settings can come really handy when doing initial bulk loading, and then moving to more streamlined updating to improve the bulk loading perf.
More settings that can be updated are planned. Ping if you want specific ones (assuming they can be implemented, and they are index level settings).
-shay.banon