so, there's nothing stopping you even in the old live SR from doing that. lane swap is a viable strategy. i've done it in ranked and in normals. if everyone gets on board then it can go really well. hell i even went ap mid and went 1 v 2 in bot lane when our lanes all got counter picked. top went mid, bot went top. we stomped 'em because our top lane nunu countered their talon. i was duo queueing at the time and my friend was supporting. we had enough people onboard to make it work.
the brush isn't the issue with top lane. the bigger issue about lane swapping is that it leaves dragon more vulnerable in the early game as they can get more bodies onto it.
there's a lot of other strats available as well. lane swapping can send duo lane mid and that works well in certain situations.
i've read but never seen support helping out the jungle (though i've seen double jungle, it can work if you over extend early. the trick is to play for late game and play extra safe because their jungles will fall behind. support mid lane i've read about too.
team builder will let you try all of these out when it's released