SIMPLE CiviCRM events interface?
I looked quickly into doing this with civiCRM entity and rules integration modules (I would think this would be possible), but that seems difficult or not possible without some further customization to set the event parameters.

If you are comfortable with this type of work, I would imagine writing a short module that engages the civiCRM API to create an event on submission of a specific webform could take in the (validated) data from your simplified webform (submitted by a user, doesn't have to be staff) and create the events for you in civiCRM. Using event templates for your categories as Aidan suggested in comments would cut way down on the parameters you would have to feed in for proper configuration. See the API explorer on the relevant version of demo site as a resource for how that might be put together.

Whether doing that work is actually worth it for your use-case, I can't answer for you, depends on how much better it is to have all user events in civiCRM (but I think it would be pretty cool!).