Gold coins under our pseudos is an easily configurable feature of SMF. I think I have read (maybe in the Staff section) that Theymos reworked the reports page, so that's probably why it's not as easy to put those reporters badges and may require a lot of coding effort.
It's not a bad idea if it doesn't require too much work and can be easily applied, but it might even be easier to add custom text to the profile
"Top Reporter of 2020", as is the case with those who have a VIP, Donator or Copper Member title below the name. Perhaps this recognition could be transitional and awarded each year to those on the list of top reporters.