I don't think this is a bad idea.
However, I think most people don't have any idea what paid support contracts usually cost. For most software packages we use at work, the support contract is the most significant cost. The support contract on our Digital Media Asset Management system (which is less complex and powerful than MC in many ways) is, ~$35,000 annually, for example. I wonder if this would be perceived as a bad thing by consumers when they find out the support contract costs (making a number up out of thin air) $600 per year.
You could reduce this cost by limiting the number of tickets the customer is able to create, but this could also create a kind of perverse incentive to "bundle" problems, making the actual tickets much more complex.
So... It could help, but the path there isn't entirely clear. Plus it would take a fair bit of analysis to figure out what you'd have to charge to pay for the increased support burden (hiring new people, etc).