Let me rephase:

I have a database that is well-normalized. I have a group whose refusal to work with me is resulting in me being forced to ignore the normalization of my database and the potential error-catching. Thus, how do I neuter a well-normalized database?

You need to get your manager / director / CTO to lean very heavily on this other group and explain to them (using very small words) that their refusal to work within the defined process is counter-productive and will shoot them in the foot in the very near future.

Barring that, drop and reload the database every time you get a new file. If nothing else, it'll be a good goad on the group. (And, it'll feel amazing every time you know that group just lost data. *mhwahahaha*)

In other words, there is no good technical fix for people who refuse to follow the good technical solution that is already provided.