Ongoing exclusion lists for a smart campaign?
We use smart campaigns to trigger an email flow based off of a contact taking certain actions. For example, they request a credit card trial -> they are sent a series of emails informing them how much they have left in the trial. HOWEVER, if at any point during this series of emails they pay us, we want them to drop from the flow. I haven't found an elegant way to do this in Marketo. I've only found three ways to do this:
1. Create a smart list that contains everyone who has paid us, then before every email in the flow, have a remove from flow option that removes them from the flow they are in if they are now in the smart list that contains all payments.
2. Use send email "options" to not send an email if they are now in the smart list that contains all payments.
3. Have a separate smart campaign that watches for payments as a trigger and then removes from the trial flow when that happens.
Each of these 3 options works, but none are very scalable, as they quickly become overwhelmingly complicated when you have multiple exclusion parameters.
What I'm really missing is the ability to set "if contact no longer meets requirements of initial smart list, remove from flow immediately" or the ability to have some program or smart campaign level "exclusion list" where I can say if contact becomes a member of this smart list, remove them from said smart campaign.
Any ideas would be appreciated. Thanks!