Spinning is unfortunately not simple, especially if you have a number of different processes going on producing different torques and a moving center of gravity. Pumping liquids between tanks is the most elegant solution, but still not simple or lightweight.

Then you have to station-keep whilst under the gravitation influence of multiple bodies whilst shipments are arriving and departing, imparting various momentums and torques. Can be done, just math and lots of propellant.

Solar furnace I'm not fond of - throughput is lol-worthy small, and you have wear and tear on seals.

You're absolutely right re nickel, but I'm unaware of any asteroid deposits of native precious metals, I understand they're all likely alloyed with nickel and iron. They could be separated out, my boss is a big fan of nickel carbonyl solvation. But huge capex and unattractive energy cost, and ongoing leakage of process gases.

I fear asteroid mining is something of an "altcoin", to put it politely.