Did you consider adding some SPI RAM chips for swapping? I think that would be the bomb.
Did you find out anything from periferal hardware, how it can be addressed without using SDK (and which we didn't already know ).
Do you know how to change the CPU speed to above 160 Mhz? I did find some hints here and there but nowhere it's described exactly how to do it (i.e. where the PLL registers are and how to program them).