Huh. One option is this;
I agree this is one of the better ways to do it. Another way I've done this in the past is creating a "parent" program that is a nurture program with event programs that nest under it. In the nurture program we hosted the landing page with a custom form that dropped down the date of all the upcoming webinars to choose from. Each date triggered the child programs if someone registered. This can get complicated but will get the job down and allow the individual event IDs to still tie only to the child campaigns and allow your attendee and no shows to map over with a sync correctly.
We have created 2-3 sets of recurring webinars (Daily, Weekly and Bi-weekly) for one of our clients. We created a single form with a separate pop-up field which shows upcoming webinar dates. Although the functionality which we have used allows to choose only one date, but through custom coding it can be made possible for a user to choose more than one date at a time.
Just set one of these up myself for the first time last week for a set of three different webinars we were offering. I created a custom string field in Marketo specific for the set of events and three separate webinar event programs in Marketo. Then on the sign-up form I used a multi select checkbox for the newly created field. I created three unique selections, one for each webinar, each starting with the date of the event. So for example....
 Oct. 21st Webinar
 Oct. 22nd Webinar
 Oct. 23rd Webinar
Then for the smart campaign it filtered in anyone who completed the form. And then in the flow depending on whether or not the string field contained 21st, 22nd, 23rd it would route accordingly to the appropriate webinar event program, changing their status in that campaign to registered. So, if the field contained 22nd their status in the webinar program for the 22nd would change to registered.
Hope this helps - it's worked very well for us so far and we'll continue to follow the same outline moving forward!
We've done this same thing too. I leverage tokens in the parent campaign to then fill in all the appropriate details in the sub-programs to save some time.