I have developed two different checklists for use when an ISV is migrating to SaaS. One checklist is for Go To Market tasks and the other is for Customer Support.
The Go To Market Checklist, in addition to being for an ISV that is migrating to SaaS, is also for an ISV which potentially has both a SaaS and licensed version of the software. Both of the checklists these are beyond the normal operations of customer support and normal go to market activities for a licensed product and both are intended to help you think about the differences in the business models.
Because the customer support model for SaaS is so different what I have seen be the most successful is a separate customer support organization for SaaS. Typically customer support in an ISV is more technical support and is IT and engineering oriented. Customer support for SaaS tends to be more oriented toward business users and how the software is used, not resolving technical problems.
I have included downloadable copies of the checklists at the bottom of the webpages and I hope that you find these checklists useful.