Can installs of KAV, BUDR, KES and other add-ons be scheduled through policies?
This is not possible. The issue here is that before KAV, KES or BUDR can be installed, various things have to have happened, for example the Baseline Audit
If you were to put the add-on installs in the policy, it would run as soon as the machine enters the view, even if the machine has not completed the pre-requisites.
For this reason, the installs of add-on modules cannot be done through policies currently.