There are advantages in booking this large group in the way you suggest- luggage allowance for example.

But there are also advantages of booking it as a proper group such as likely discount (you won't know what it would be until you ask and you can ask BA to do you a quote with no committment on your side) and the ability to change the names of passengers up until something like 14 days before the flight. Handy if Fred and Freda can't go but John and June decide they want to. Booking it your way would mean F&F getting very little back if they did cancel but as a group booking J&J can just pay F&F what they paid and you just swap the names on the group booking.