In GrowthExperiments we are using morelikethis as an approximation of topic search. It would be nice to be able to do (...) morelikethis:A|B morelikethis:X|Y and get a result set which is a mix of articles similar to A or B and articles similar to X or Y. What often ends up happening is that one of the morelikethis article sets ends up more "powerful" then the other, so all results are via A/B (or the other way around).

One way to address this would be to allow weighted morelike queries: we'd pre-calculate the top scores for (...) morelikethis:A|B and (...) morelikethis:X|Y (the (...) can only take a limited number of values) and use them as inverse weights, with something like (...) morelikethis:A^0.7|B^0.7 morelikethis:X^0.3|Y^0.3.