Recently someone else came up with this idea, and I thought I could share it.
Basically roleplays would get an extra option below the message, being to "like" it (like on Facebook, yes). This would encourage people to roleplay, because they actually get some credit for their work. Also, it would allow people who enjoy reading roleplays (but not necessarily enjoy writing them) to express their intrest.
Advantage
This would encourage roleplaying, bringing BM to life
Disadvantage
Is in analogy to Facebook, might disrupt IC'ness. (though an option to show/hide the button and stats could be made available)