If you're thinking about something generic (e.g. that would work for any filetype), this has some serious drawbacks, mainly coming from the fact that most filetypes are identified by the first bytes inside the file (sometimes with some complexity). So it would require:
- To read something like 32/64 bytes of every file in every folder you'd open. This would have an impact on performance, especially with large folders.
- Directory Opus to implement (and update) all the filetypes magic numbers (those first bytes) in order to be able to compare them to the extension provided.
IMHO, you're better off targetting the most frequent filetypes people are sending you with wrong extension, and put in place a way to check only these files, triggering that with a user action (a button, a column).
As an example of this, you can have a look at a small include script I shared recently that checks a file extension against its magic number for common image file types ... Include script for image type detection based on magic numbers