Honestly, trusting the Lowest Elo Player to do whatever role they want to do isn't the best plan.
And if they're a good sport about it, they'll play whatever they want. If anyone wants to be a good team player, you build around your team.
That's the way I look at it anyway.
I sometimes plays support as 1st/3rd pick just because I simply do not want to trust the lowest Elo player to do it. Sure it isn't the most enjoyable role for me, but I can sure as hell play it better that someone who doesn't want it.