To start with: a variant of FizzBuzz (string manipulation, sorting, fibonacci etc). We then combine this with plagiarism checker and code playback for the employer. Which gives them a pretty good signal if to set up an interview or not.

That seems reasonable as far as time commitment. But, problems like that typically have about 2-4 ways to code them, and usually 1-2 obvious ways. Not to mention, it’s going to be a max of maybe 25 lines of code. That makes me skeptical of the plagiarism detector, because it seems like it would either not detect much, or it could end up being overly sensitive.