Ok, Had a better look at that Allwinners pinout, and i would say definitely on 4-6 layer. Almost all the center is taken up by the grounds and power planes, meaning you have your decoupling on the far side and happy days. Leaving you with roughly 4 balls deep at any point around the chip with plenty of missing pads to allow for some routing cleverness. which would be only 2 signal layers to escape. e.g. on a 4 layer, Signal - GND - GND / Plane - Signal. you would just make sure on the 4th your signals had a clear ground return path.
A part of me feels tempted to try and fan out this BGA on 1 signal layer, but I'm going to have to call it a night. Its so much easier at 4/4 rule.