Tying to differentiate content access - trial v post-trial periods

I have a site (s2MemberPro) which sells access to content with monthly, quarterly and annual memberships. I am using custom capabilities (CC) to restrict access to certain high value content and LOVE this feature!

To encourage new members I would like to introduce a free trial membership. I understand this is a fairly standard thing to do but I have 50+ webinars I do NOT want these trial members to be able to access. On my prior website (Drupal) people would join for the free trial and immediately download everything! I can edit each of the 50 webinars to include ‘NotATrialMember’ as a CC meaning only members WITH that CC can access these webinars.

So, the question is this…is it possible to have these people sign up for, say $0.01 for the first seven days and during that period they do not have this CC. However, when they are subsequently billed $xx for the next month/quarter etc they are automatically awarded the CC meaning they can now access the webinars?

Any input much appreciated.