Yeah, anti-seize is mandatory on assembly with stainless to prevent galling. Figured that out the hard way some time ago.
I have greaseable bolts now, so you can see how on top of maintenance I've been. I think I tried pushing grease in at some point but it must not have had anywhere to go because it mostly just ended up pushing out around the zerk.
I'm no metallurgist, but I think it all boils down to alloy selection and picking one that is somewhat corrosion resistant but that can be hardened. That is the problem with the 316 stuff at the hardware store, it's not heat treated plus actually doesn't perform all that good in the absence of air. I've pulled out bolts from rails of WilderNests that have a ring of rust around them where the bed rail foam had trapped gunk.
Like you say a 17-4 or maybe 4xx series stainless.
I think there is a stainless that will work, they use stainless fasteners all over in ships and breweries. Obviously cost is a major reason why you don't see them used normally. Just takes the knuckleheads once in a while pulling out bolts and recoat them to keep them from rusting in place.