How can we improve WHMCS?

unpaid invoices must be deleted after certain time when they are not paid and also the relevant domain-product services should be deleted, under present state what happens is if i have a reseller with mulitple domains under me invoices keeps getting generated and we need to manually search for the domain that has not be renewed and remove the invoices as the clutter go long and long day after day. this falls true in case of products and services too. so simply if an invoice is not being paid for say 90 days it should be deleted and the and the product or service associated shall also be deleted upon approval.