I know it's a little late to weigh in but anyway...

If I tried to use a welder in my current workspace my wife would beat me to a bloody pulp. Whatever I use there has to be built in situ so I can't weld it up outside and bring it in. Oh and I don't have a welder and I have no idea how to use one if I did! Using profile I can easily get it up into the workshop and work on it.

While steel may be a better material for the mill itself, alu can be a better material for the shedless city dweller with a converted attic for a workshop