Ability to Auto Delete Pro-Sites after X Duration

I swear this has been discussed before but I cannot find it. But currently we have over 465 Sites running with Pro-Sites...of that I would say 1/3 are non-active pro-sites. This is problematic as right now our Wordpress Database has over 13,000 Tables...not records...tables. So the system is starting to run sluggishly slow. Currently the only way to thin out the database is to manually go in, check each site that is not subscribed, see how long they have not paid and then delete them...we are talking hours of time just to delete sites. Is there any way to automatically delete a pro-site once it has been expired for longer than 2 months? Have it send them out one final warning a week before it deletes stating "due to your site being expired longer than 2 months, this is your last chance to renew before the site is deleted permanently."

Right now this is very frustrating and using up valuable resources to handle something so annoying.

The other issue is the fact that load times are getting worse and worse the more sites we load onto it...there has to be a better solution other than "increase your server size"