Ranking results from a multiple index search?

I currently have 4 indices (one per DB table as is recommended here).

When submitting a search I’m doing a multipleQueries query to search all indices but the problem is that in the result set each index is ranked and returns its own facets which then have to be combined somehow before being displayed.

Is there a way to specify a global ranking strategy when searching to avoid doing that manually after getting the results?