Today we map each field in a Elasticsearch document field. If the bridge is the same, that means we copy the same data twice unnecessarily in the Elasticsearch document.

Elasticsearch has the option to define multiple mappings for a given document attribute via the "fields" feature
https://www.elastic.co/guide/en/elasticsearch/reference/2.3/multi-fields.html

The drawback is that it cannot be done for different fieldbridges as the output might be different.
Also it does not necessarily align with our naming conventions: they use nested properties for additional fields e.g. title and title.raw where we tend to do title and title_raw

My gut feeling is that it's a lot of twists for a minor alignment and it should not be implemented.