Allen Bradley Plc Programmer

I own an automation company…my company normally uses wago with programs written in Codesys. My customer has hundreds of existing I/o done in Allen Bradley Flex I/o . I would like to use my EXISTING complex Codesys program running on the wago to the control the existing Allen Bradley flex I/0 at my customers site so they do not need to be all disconnected and retired…I am told it is not so easy…as the two brands are not compatible…Thus, I need an extreme expert to figure out how to make it happen..