Honestly
Sometimes the right answer is to keep what you have
Replacing a SaaS product is the request we most often advise against. If a product is genuinely deep in a domain you do not want to own — payroll compliance, tax logic, clinical coding, regulated calculations that change every year — buy the product. If your seat count is small, the subscription is simply cheaper than any build, however efficient. If your requirements are still moving, the subscription is buying you the option to change your mind, and that has real value.
An opportunity assessment is designed to establish which of those you are in before you commit, not after. Sometimes its conclusion is that you should keep paying the subscription. That is a useful answer, and it is far cheaper to reach before a build than after one.