You would need a lot more hands-on moderation than other communities, since it would be harder to build a self-governing community like HN that largely knows who to mod up and who to mod down.
In principle, but you could do things like making an upvote within a clique mean a lot less than an upvote to somebody you haven't agreed with in the past; give additional weight to people who often vote outside their own cliques (so as to reward those who have a more balanced view); letting stories initial weight depend on the previous balancedness of the source, optionally make it gain points fast if it gets upvotes from those who wouldn't normally upvote stories from that source. There are endless improvements that could be made. As a side effect you are likely to get more interesting discussions precisely because you go for the more "unusual" stories.
