In addition to the not starting more than 50% of the games you play in can the other qualifier be that you cannot be in the top 5 of minutes played on your team during the year?
In the last 15 seasons one two players have won the award meeting this requirement (Brogdon and 2014-15 Lou Williams)
I just feel like this would capture the essence of the award without caveating players that are top 5 minutes but either injury or lineup staggering have them qualifying
Using total minutes make no sense. A mid-season trade for example could mean the 6th man actually has the 5th most total minutes.