Lima Beans mentioned one coming in 2009. It's 2014.
http://forums.na.leagueoflegends.com/board/showthread.php?p=358084#post358084
In the meantime till this comes out, why can't a UI flip or UI disabler be implemented that can be turned on and off with a keystroke? It doesn't seem too hard to implement.
How about making the orientation of the nexuses be in the same position as in Twisted Treeline. As in, rotate the map 45 degrees so the nexuses are on the left and right sides, mid goes horizontally down the middle and top and bot go at 45 degree angles. Would that work? Or would terrain block vision? Would it be super awkward to play with? Or would it just need time to get used to? I think this makes the map easier to see for both sides. Also, in this orientation, if Riot still wanted to add a "flip" option, they could just flip the map along the Y axis for purple side, instead of rotating the map 180 degrees. This keeps the top lane at the top of the map, and bot lane at the bottom. Just a thought.
The map fundamentally does not work that way. There is no rear to most of the map graphics, so reversing it would have the level of work of making a whole new map. Moreover, it would add needless confusion to the terms "bot" and "top", which are incredibly well-established among all levels of the playerbase. It might even create balance issues of its own.
I think it's based on riot's roots as a mod for a dota game. The original map was arranged in such a way and they don't want to stray too far from their roots.
Or maybe they haven't made the back half of the map and will make an option for that if they ever update the map again
if ou play screen unlocked there really is not much of a problem but with every thing in game favoring the blue side this really does need to happen in one way or another i do think that i read somewhere that they are planing another rework of the map and that they were considering doing it in the same position as twisted tree line. the map is angled wrong to do a just a flip and there is no back animation as listed but they should think about it to level the playing field for those who have not learned to play unlocked.
