duplicate SKU issue

I have been selling on Amazon for a while and there is a long lasting issue with creating duplicate SKU. Issue is as follows:

Let's say we have an inventory for ASIN XYZ with SKU 123. We wanted to add an other offer for same the ASIN with different SKU but accidentally put 123 as SKU. Now Amazon confuses things. Even though after submission it says it is a duplicate SKU bluh bluh it already messed up your original offer at FBA inventory. Every time I make a mistake I need to go through multiple rounds of customer service conversations to get them fix this.

I propose a pipeline where submitting a duplicate SKU is not allowed at the beginning before it messes up anything.

Best