Ask before committing
Before selecting a system, describe what changing your mind would involve. Not because a change is inevitable, but because that description reveals dependencies that an implementation plan can leave invisible. Consider data, processes, integrations, skills and operating arrangements separately.
Export is not the same as portability
Imagine receiving every file and database record tomorrow. Could another team interpret them? Are identifiers, relationships, attachments, permissions and history included? Do the formats carry enough meaning to reconstruct a useful service? These are questions to investigate with a sample, not promises to accept without a test.
Remember the organisation
A technical migration can still fail as a transition if nobody has time to reconcile records, redesign workflows or learn the replacement. Record the work that falls to users and administrators as well as the supplier. Who can explain why the current configuration looks the way it does?
Rehearse one small exit
Pick a representative dataset and one complete workflow. Export it, document it and try to use it independently of the original system. List everything you needed that was not part of the export. That list is a practical starting point for a discussion about dependency.
A question to take away
What would we need to know, retain or negotiate now to make a future change a decision rather than a crisis?