stacking them is duck soup, it's part of the plan and another of the many positives about container homes above any other option.  you can go at least 3 stories high and even more as the foundation expands, plus it automatically provides shade for the units below and less cooling expenses while making the entire complex sturdy enuf to withstand a hurricane. try that with any alternative structures. this proven concept is ages old already, we don't need to figure out nothing other than getting past systemic ignorance and obstruction.
''otherwise it takes up too much space''
nope, if the State can instantly come up with vast acreage for a rebuilt internment camp Disneyland full of barracks which won't house a single soul then we can do this multiple times to house the 15,000 Oahu homeless permanently.
the ways abound, but the will is non-existent.