We've just been playing about with creating menu items that use the event list by category type. That's perfect because, as you say, you can assign modules and menus to menu items. If you can get the Upcoming Events mod to behave in a similar way that would be grand
I'm not sure if it helps you...
I noticed that despite the fact you are using JRoute::_() on the category link in the upcoming events, it doesn't display a SEF URL.
It displays as
/component/dtregister/?task=category&category=5&Itemid=
If I create a menu item of type Category List of Events the link generated is like
index.php?option=com_dtregister&view=event&layout=categorylist&controller=event&task=category&list1=5
Which then displays as a SEF link on our site...
training-schedule-list/course-calendar-excel
I am learning about this as I go so that may not help
Great support from you guys btw.