The only way to get a true idea of what the members want is to do a survey of every club member who wants to have an opinion. Put it to the clubs in the NZACA Newsletter with exactly that question.
"In future Nationals competitions, should the use of water craft be included with 4x4 and motorcycles as a means of accessing land based locations?"
Let the members have their say. If the numbers come back anything more than even, then the option has to be put in place as a discussion piece. Anything less than half would mean majority rules and it stays as is.