I know they are different protocols, but presumably, one app is not fundamentally restricted to one, is it?
I think such an app should not be called DAVdroid because that would confuse users (like me before I investigated the differences).
There are some public calendars (like concerts events) that don’t have reminders and you can’t control the source, so it is impossible to set a reminder for now. For those it would be super helpful if you can set some fixed reminders (yes, more than one ideally) for all events in a particular ICS calendar. So I can set to get reminders for all concerts the day before and 2 hours before the event for example.