I agree. Bubbles shouldn't be given to maps the community hasn't looked at much. (Yes, the mapper could kd-star spam, but if they have the kd they probably have a reason to push their map so much.)
I'm not sure if the current 8 star limit is for bubbling or ranking, but I think it'd be best to have a much higher limit for bubbling. 20 or 25 seems reasonable. A top N may work too (currently a +20 priority map has 72 maps ahead of it); top 50 seems pretty reasonable (if the top 50 includes current bubbles), so if the standard shifts so does the bubbling limit.