NSA has (had?)a 'twinning' rule rather a DP/FLEX which allows this. I haven't done NSA in 4 or 5 years so not sure if they still have it. Basically it is 2 players in one spot in the lineup and you could exchange them however you wanted how many times you wanted.
NCAA tried the “twinning” concept one year not too long ago during fall ball just to see how it would work. The fact that it didn’t make it into the rule book for regular season play spoke volumes on its popularity.
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