In the coral heads in tropical waters, you can only reliably navigate visually. You can't do that from the deck very well, way easier from the spreaders. You almost have to have steps to the spreaders to make it easy to get up there to see the lumps.

We drilled and tapped the fasteners for our stainless steel steps and used LocTite as a thread insulator. We just used a hand tap which I assume is a cutting tap. No insulation between the steps and the mast. Nearly 35 years later, the steps are still there and the mast hasn't suffered for them. If you are concerned, put electrical tape where the SS touches the mast. The second owner of the boat had the mast repainted because of general deteriorataton of the paint, not the steps. He thanked me for using screws as fastners. It made stripping the mast way easier. I wasn't thinking that when I did it as tapping six holes for each of the steps was really a long involved process. I just didn't/don't really trust pop rivets.

Stainless Steel is close enough on the galvanic scale that it is not a great problem on a mast. I've stripped most of the hardware off the 40 year old mast on my current boat. The hardware was fastened with SS machine screws and I got all but one out without drilling. Doubt the fasteners were originally done with an antiseize compound as none of the fasteners came out easily, love that battery powered impact screwdriver. All the threads in the aluminum were still good and refastened most of the hardware with TefGel on reassembly. The masthead is stainless steel and was not a problem. Did have some galvanic deterioration with the bronze goose neck track that looked to have been installed without insulation material. Fortunately, the bronze winch bases were insulated with a thin plastic.

Did I read that you are planning on using 1/4x20 fasteners?? #10 fasteners should be plenty big enough and a bit faster to install.