It would have been easier, yes, although I'd like to have had the other 2 data bus pins too (if I had to choose between the two I'd pick the data bus pins)
I'm not sure how worthwhile a memory expansion would be commercially, given that there's already quite a lot of ram in the Due, and there's always the Raspberry Pi for applications needing huge of memory. But it's an interesting enough project if you've already got an old SRAM chip 