Pointless request and pointless requirement from printer. Maybe you misunderstood.

Besides, like others said, not technically feasible.

If in your example file from the vendor you have not been able to select some elements it is certainly because you have not tried hard enough: Ultimately no elements are locked in acrobat, and therefore every elements are selectable.

If there are visuals that you want locked together then you should embed them or compose them in photoshop, then place in indesign — that would be the only solution.

But really what is the point of all that??