However it pans out, the firm intention (AIUI) is that existing Calendar events will not be impacted in any way. Whatever is done, is done to work around the events.
Regarding reg 4.2, I would suggest that at any moment in time, you could ask "what is this rider doing at the moment?" and get the answer, either "an event" or "a permanent". Its two separate organisers, two separate cards, two separate validations. Yes, we might need a new sub-class of Perm to handle this, but that happened when DIYs were introduced as well, without any need for regulation change.