Nurture Program Based on SFDC Custom Object

We have a freemium model that will drive large volumes of users trying our product - ideally leading to purchase.  Our SFDC deployment has key user details in custom objects that have a many to one relationship with the SFDC Contact object.  We want to trigger different nurturing activities off changes to these custom objects.  Unfortunately each time we add a new variable, we need to remove and replace all variable from each program/campaign - which will only get more complicated as we grow.

Any ideas on how to structurally set up an architecture where there is not this 'rework' that has to be done when adding new fields?

Larry