I was sent here by Riot Support (Kunoichi). :) I sent them this and they said I should post it here:
"*I switch between the roles of support and marksman a lot, and it bothers me to go into the menu, and turn off autoattack every time I switch to support.
Can i make a button on my keyboard do the job for me?*"
I'm glad i could give a suggestion, that might just be a part of the game a few patches afterwards.