A rain screen is a must with steel panels. They condense moisture, which you do not want in your wall. The moisture needs somewhere to go, and so a rain screen is the only option. Where corners are concerned, there are many options: you can have a bent plate to create a clean corner, or you can reverse a bent plate to have a recessed corner. If I were you I would hire a local architect to help you with detailing. This is not a standard method of construction and good detailing will save you thousands of dollars down the road.

Best of luck.

Many municipalities prohibit steel siding. Better triple check. This is gonna be a heck of a LOT more expensive than vinyl before it is all said and done.

Everything is more expensive than Vinyl.

Why would a municipality prohibit steel as an exterior finish? I've heard of corrugated metal panels being prohibited in certain districts, like a historic district, but I've never seen steel specifically called out as a prohibited material. Can you provide examples?