With reattachment the only valid solution is to generally (re)obtain the loaded state. This might happen in a number of ways:

• The enhancement option works if we have the entity track its state. This is already true in the new enhancement code I am working on. The next piece there would be to have that state become part of the entity's serialized state as well (currently I have all the enhanced additions set to be transient to not muck with the managed class's serial signature)
• (re)load the loaded state. Part of that could be to peek into the second level cache as a first option, before physically querying the database. Personally, I'd like to see select-before-update control this; or maybe we default select-before-update to true for entities which contain one-to-one associations with orphan-removal enabled. But even then, currently select-before-update is too late in being applied to help here, so we'd then also need to add the ability for that loading to be triggered here.