So the teams that made it to the FCS (formerly D-1AA) championship game in football played 15 games (JMU) and 16 games (Youngstown State) and that is with a 24 team playoff system.
Alabama and Clemson both played 15 games with a 4 team playoff system.
Adding a 16 team playoff would make it a 17 game season (for those teams that advance to the finals)..which really isn't THAT much more (I get the argument that these are 18-22 year olds who need rest/recovery).
It has been mentioned that the only way this works is to reduce the schedule, but I don't see that happening. Too much TV and revenue generated.
A lot of your smaller schools (including JMU and YSU) usually play at least one "Power Five" school, on the road, basically to make their athletic budget look better. Most of the time it results in a loss, but it's all about the bottom line to ALL involved. The smaller schools gets the check and the P5 school gets a W, gets another home date to sell 65,000+ tickets to (or force it into the season ticket package) and it becomes a chance to get your 2nd strings some playing time.