Team Builder draft pick.

I love the team builder concept "great i only have to play the roles i want = more fun". But why do i have to select everything in advance why cant we have draft pick? Could we not just select a role/position Eg.jungle, support, Top and be put into someones team to fill that role and once we have the roles enter a normal draft pick ,picks and bans phase?, Everyone will already know what role they are in for and it allows Draft pick which although it may not be viable yet would also mean you could do something similar for ranked games.

Team builder seems great knowing you have a proper team everyone plays what they want ect. but i far prefer draft pick as a game mode. Maybe everyone else doesn't agree but id like to atleast hear some thoughts.