pretty sure all that would be necessary is to use the server var, i.e.
at the moment this gives an "unknown command," which may well be that way on purpose for various reasons. after setting such a variable, if it were possible, it would probably be necessary to /resetconfig, unless the game did this automatically when a server var was set.
it's already possible to save a server's vars locally in a server format with /writevars "namehere.cfg" 1 1
all you'd need is an automatic way to update your server's init with this file (which i'm sure is possible one way or another).
then a /resetconfig and you wouldn't even need to restart the server
i as well would only recommend the setting of sv_ vars being implemented (if it's even possible) for global/local admins or above. (there may be cases where a server has set an abusive setting for players, and higher-ups should have authority/ability to change this, it's their prerogative).