Ideas should have required custom fields

We use our idea portal internally in our organization to collect and track one-off feature requests that aren't part of a larger project.  I have a "severity" custom field in this Idea portal and I would like to make it required input for my users, however, as far as I can tell there is no way to do that.

While is is a feature that we can live without, it would immensely improve the quality of the input that I receive on our idea portal.