Wouldn't it be best to just make your own import workflow, that does any of the checks you want... and errors to the user if the filename is wrong? (or changes it to make it "right"). Then you can change the import command to call your workflow instead of the default one..
Are you certain it'll be that much better than TS Widget though?
I want to validate the file name when the file is imported to teamsite using file import GUI. But I cannot found any options to config this, so please advise me if you have any comment. Thanks!