Some things need no new feature, just a trick in the calendar you already have.
Registration deadline
Create a second, all-day event on the deadline day, such as "Registration deadline: summer camp", and add the link to your registration form under "Links & additional value". The deadline then lands in every subscriber's calendar.
A backup date for bad weather
Put the backup date in the title ("Club fair – if it rains: 14 June") or create it as a second event. Once decided, cancel the event that is off instead of deleting it: Cancel an event.
Clubhouse or hall bookings
A calendar of its own, "clubhouse booking" with entries marked "booked", is often enough – without private names, with a contact person on your account page. Link it in the training schedule under "Trainingsfreie Zeiten" (times without training) and affected sessions drop out automatically.
Taking over a yearly schedule
If your programme exists as a poster or PDF, "Recognise events" reads the events out; as a file (ICS, CSV, Excel) use Importing events. Weekly training times go in via Weekly plan from a photo or PDF.
