Just an FYI as to how I ended up implementing a Hold Feature for our subscribers...

Our subscriptions are for 7 days with mandatory auto-renewal. I created a Hold Subscription Plan (free for 1 week, then expires, no auto-renewal) that is only available as an upgrade to users with an active paid subscription.

Now subscribers can change/upgrade to the (free) Hold Subscription Plan that expires after 7 days. The expiration letter is then triggered saying... This is a friendly reminder that your subscription has been on hold for 7 days. You must resubscribe to restart your service......