Yes a string in the EECH.ini could be a good solution.
I don't know if it's easy to do and as far as I've seen the KA-50 is the only helo with mirrors at the moment, so it's questionable if it makes sense for this single helo only.
But maybe it could also be a benefit for later addon helicopters like the CH-53, MI-8 / MI-17 or something else.