I think one answer would be to make it a double season progressive years before the present day. For example: for the 2008 draft, you would add players from 1962. You could even make it "rookies only for players drafted from 1962-1968" so as to not flood the draft pool. All players would progress 1 season at a time like normal and then when the league catches up to the present day, all of the 2015 players would drop off the next season and all the 1968 players would progress to 1969. The 1969 draft would then be a single season draft. (rookies and non-rookies alike)