This might work well in some situations (e.g. research, development), however it would also increase the effect of echo chambers I think.
Google's not exactly working against the echo chamber problem, and I think that's because to do so would be to work against its own reason for existing. There are two goals here that are fundamentally at odds with each other:
1) Finding what you're looking for.
2) Finding a new perspective on something.
A search engine's job is to address the first challenge: finding something that the user is looking for. The search engine might end up serving both needs if they're looking for a new perspective on something, but if these two goals ever come into conflict with each other the search engine does (and I would argue it should) choose the first goal. Failing to do so will just lead to people ignoring the results.
If you're indexing forums or social media, the same site is going to give back the bubbled responses, possibly without the person even being aware they're in a bubble.
https://www.google.com/search?q=%22BATF%22+guns&client=safar...
https://www.google.com/search?q=%22ATF%22+guns&client=safari...
Interestingly, back then, Google was big on neutrality and refused to do anything, stating that it reflected the way people used the word. It was finally addressed using "Google bombing" techniques. Something that Google didn't care much about back them because of its low impact.