We need the ability to gather a family's dependents Level height(s) (both Absolute - from the Surveyor Point and Project Base Point), as well as the families' offset from these Levels - so that we can calculate absolute points within individual components - then schedule and tag this data. This needs to be live information - opening Dynamo and running a script every time a window height changes is unjustifiable.
Spot elevations achieve this only partially with their bottom and top heights - this approach would allow much greater flexibility. In addition, when families are edited and reloaded, often these spot elevations get deleted as it loses its host geometry (I assume) - another problem for another post.
I imagine this looking similar to how Room Information can usually be scheduled within another category, except,
of course, that this would also be available within the Tag Families' environments.
The new 2020 feature of some MEP items getting their elevation heights in schedules (as well as sill heights for windows always being there) was a good first step.
Now let's get this all the way there.