ARAM randomness

After playing numerous games of stupid offset teams, I got to thinking. Riot already has champions listed in their perspective roles (tank, support,ADC, ETC.) why not use that as a Random base? Afford each team 1 tank, 2 adc, 1 support, and a mage and randomize those roles. I like the randomness, but i hate feeling like i always get stuck on a team full of supports against a team of bruisers.