DDR3 routing: swapping data wires
Absolutely possible in generic case. We have done the same with DDR3 RAM and Intel atom processor. Unless we did shuffling the data bit order, there was no way (IMHO) to complete the optimal routing in 6 layers.

The bits gets shuffled while storing into RAM, but from processor point of view, it will remain intact.

Care should be taken, if memory is a shared  resource.