Originally Posted by ATH1337
Trolls will be trolls and can still select all 5 positions to get in game quicker. Once the game starts they will still go to the unassigned position of their liking.
Looking at other games that use a similar system, history dictates that this is not the case for the majority of players. The common player would realize he'd be intentionally compromising his team and his own chances of success by doing that, hardly a worthwhile sacrifice just to reduce the queue time a little bit, hence he will not do it.
If you are however talking about true "trolls" that don't care other than to intentionally grief their team, those will exist regardless, although they are a very small minority. The best thing to do is ignore them and report them after the game. Not being able to fix all problems however, does not mean we should ignore the ones we can fix, and this system would undoubtedly fix many problems.
This point has been brought up and answered before. There is more info on that in the opening post, please take a look if you haven't yet.