Upgrade Page for Existing Pro Sites

The Pro Site plugin generates a check-out page where we can add content to promote upgrading a non-Pro site. But while the plugin provides for numerous levels of upgrade, there is no option to create content specifically targeting existing Pro Site users with incentive to modify their account or upgrade it further.

Please consider this a request for the ability to add an "Upgrade Message". The current checkout page content shows for any non-pro site, but any Pro Site user who visits their account page only sees the upgrade options and checkout button with no content above that. The ability to add a separate message here with incentives to change their subscription plan would be a big plus!

At the very least, the same checkout page content should be shown whether a user is upgrading for the first time or modifying their subscription to take advantage of additional features. This way we could write content that addresses both scenarios, or present users with a feature comparison matrix. Having separate pages, however, would be preferred to keep content succinct and specific to each case.

I originally described this request here.

Thanks for the consideration!