if the config is strictly the same, you have a "replacement unit" option with ZTP+ (XMC 8.0+): Edit your device (configure device), and select "remove from service" and set the S/N of the "Replacement unit", once discovered, that new S/N will inherit the last archived config of the previous unit. However, I don't think it's allowed to replace a unit with a different one... and that doesn't work with stacks. Have a look at it and try it on one unit to see if it can help.