Hi Roberta,
In our shop we are using "ELEMENT LOCKING", make use of O000315A ref. SIGNIN-Action, have set SOFETCH=N in C1DEFLTS.
I believe, the intention of "ELEMENT LOCKING" is to ensure, that a CASTed package is kept executable without errors caused by interim changes to referred elements.
My vote is, that Quick-Edit may fetch a LOCKED element but must not allowed to save or modify the element so that the package becomes not faultlessly executable. This corresponds to your option "2" but even beyond: Quick-edit should fail to save or modify with an explaining error-message (C1G0503E), even when the package is not yet being executed (during the whole period of time, the element is locked).
Kind regards,
Josef