When creating a board calendar event it would be great to have the option for board users to sign up to the event as confirmed tentative or reject.
At the minute we've no plans to include the calendar in the core due to its limited usefulness. We do have a plan to start offering official plugins created and maintained by the MyBB team, which will likely include a calendar. In that case, the calendar would likely be much more fully featured and would include things such as participants and invites I would assume.
That would be fantastic... It would fit both worlds lighter core but more robust and fully featured components that users could choose to implement
Yes, totally fine to not include the calender in core.