If I think of this as a CSE, I would see this as a troubleshooting problem. I probably wouldn't want to give them a macro that purports to pull in any kind of Excel file and reconcile mismatching schemas because then I would wind up having to support the macro (and answer questions like why column 23 is a string instead of a double). So my solution is a workflow that fixes the specific issues with the files. The CREW macro might also be an option as long as the CSE explains what the problem is and points out that the CREW macro does change all the data types to strings.
With that said, I'm still having trouble getting my head around batch macros and reviewing these solutions was very helpful.