malabo,
I know that in FAA-land, maintenance ferry flights with less than perfect machines is allowed, as long as the operator has approved procedures for the operation, flies a route that does not endanger the public, and has FAA FSDO approval. I signed several such ferry letters (the procedure part of the equation) for S-76 operators in the past.
The "repairs" you speak of could be performed afterward, as long as a good inspection showed airworthiness, albeit with one fuel cell. It is also possible to carry a new sponson to the rig and replace it there. The sponson can be removed and replaced in a few hours. The people who are listed on the repair station license can perform the repairs elsewhere as long as the regulators agree. The idea that only the repair station roof covers the approved repair station is a bit quaint.