The following case is now impossible: I want to save an existing motion and I want to get a new version without changes of the version data just because of a actual time stamp. The (at the moment not existing) feature might be a confirmation of a version on a specific point in time.

Can you choose a more explicit way: If I set use_version manually to a new version, then I want to get a new one. If I care about whether data has changed, I can use your new checking method before.