Not lose your data in Prod model when you change a list from Structural to Production and sync

List A was Structural in dev and prod models. I now want to have list A as production so change it in the dev and sync with Prod. The problem is that as a result I lose my list items in prod model. So when this move from Structural to Production list happens, I would like to be asked whether I want to keep my data as it is in the prod model (keep the list as it is but make it production data) or not.

Benefit: that would avoid loosing all my data stored against the list if I decide that a list I have been using for some time has to be changed to Production data.