Hello Mike,
Of course you can use SO-DIMM modules for your design but it is not possible to change the timing behaviour during run-time with the SDRAM controller of the Nios II. Perhaps there are other vendors which provides SDRAM controller to do such things.
One solution is to set worst-case timings in SOPC builder and use these for all modules. Or you do the settings for a specific module and sell the board only with theses modules.
Using SO-DIMM modules is a good idea but it is also possible that you won’t get these modules after some years because all new notebooks are using DDR or the price is very high (like with the normal SDRAM modules now). But that is only my opinion. Perhaps some others have more detailed information.
Bye,
niosIIuser