Need ability to set system-wide defaults to limit spaces used to generate the Recommended Updates email

We need to be able to limit (at the system level) the spaces that are used to generate the Recommended Updates email. We have a fair number of spaces that are full of customer documentation which are automatically deleted / regenerated every few hours by a number of scripts. All of the people receiving the email don't want it as it is really useless as the email contains only links to those autogenerated pages.

It would be exceptionally helpful to be able to limit which spaces are, by default, used to generate the email. Otherwise, our only option is to disable the Recommended Updates email for all users.