Prestige bonus(es)
Gaining a prestige level should grant you a stackable bonus of 5% BP gains from matches. By the time you hit P3, you'll gain a 15% increase in BP gains. The % can be tweaked to be higher of course.
There may be other bonuses out there too that could go along with being prestiged on your character other than a rather dull cosmetic.
Comments
First of all, increase BP gains by 7-10% as is; the grind is ridiculous.
Secondly, I really like this idea, it gives strong incentive to prestige (as it currently does nothing).
Good idea, would prefer 10% at least per prestige though.