No, this is not possible, I'm afraid. This would require to also refresh mappings and session. By design, Informatica Source/Target definitions are not related with any particular implementation. This might cause a lot of issues if you'd use one mapping in multiple session to access many different servers. If one of them would change, this would impact every other one.
I guess you can have some additional session that would perform simple read operation to make sure the structure has not been modified before actually starting the main ETL part.
Well, to be honest: other solution would be to have a tool that checks source and target definition, generates the whole mapping/session/workflow, does the import operation on repository with conflict resolution and runs the workflow afterwards. This is possible, but... very complex.