My anticipation is of this ending badly, i.e. the suitcase getting its walls pierced within a few flights. The checked-in hard-shell luggage I travel with is quite banged up but its walls can take it. I gave up on soft-walled luggage quite a while ago because it was costing too much in terms of losses - both damage and theft (some psychology had to be involved in the latter stopping with hard-shell). I am really doubtful about the plywood, but I appreciate the idea of taking the issue into one's own hands.