If your proposal was the one to use second level cache values, then no. Thats not enough in and of itself. We cannot rely on the second level cache being enabled for something to work or not; its there as a performance option.

No, with reattachment the only valid solution is to generally 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.