A multiselect option for custom course fields

The new custom course fields are great. Perhaps there is a reasonable explanation why this field type was not included, but it would be really useful for us. The requirement is to have Teachers select all the applicable campuses that a course may be available to take.

With over 10 campuses available using checkbox means the custom field display on the courses page gets very long.

There may be another solution for what I'm trying to achieve but I was thinking a multselect dropdown menu would do the trick, and then on the course page only display all those values that are selected (or not selected - a toggle for this could be in the custom field setup)