It would be great if you could continue to remap import rules when there is a change to the target data structure, rather than just getting stopped with the message:

Error validating import options The following options are not valid, fix those before importing data: Property 'xxx' doesn't exist anymore on the documenttype

In my case I have renamed a property alias on the target. It would make sense to me not to be able to just run the import from the definition again, but I think it would be better to be able to go in to edit the defintition rather than having to recreate the property on the target.