You might be surprised... I have 200A service and a highly underutilized 100A subpanel in the garage.  67A@240V is nothing!  Seriously though, that is going to be way too costly for me.  Maybe a mini-farm scale miner could do it, but it is certainly not for a nano-farm scale.

How about a 2u-3u chassis that accepts 1-4 of the same replaceable boards that the 12u uses and also uses our own PSUs?  The chassis would need to be standardized in a way that would last years and instead of replacing the entire miner every generation we would buy new boards for it (considerable savings in the future).  Due to the dimensions, it would probably have to be "some assembly required" to keep the shipping cost of the chassis down.  I'm not sure if this could be done cost effectively, but it could be an option to consider.

I'd even consider replacement boards for our SP20s instead of a whole new miner, but I imagine that would require you to spin a whole new board design and would be costly, thus the chassis suggestion (two chassis sizes, same hashing boards) might be better.