The steel moment frame, to someone with shallow knowledge, sounds so strong and resilient. But in fact, a rigid steel structure is more vulnerable to seismic (and even wind) loads than wooden framing which can flex and move and dampen those loads naturally.
The stainless spec for the frame is just pure silliness. Looking at my notes now, for steel beams buried in the ground:
200 microns of rust per year in very aggressive soils, but it rusts on both sides, so make that 400 microns.
... which also means that unburied steel, protected from elements, up in the air, is going to last more than 1000 years.
Oh, and also, the SS is more brittle so you've made your seismic issues even worse.
...
If I had an unlimited budget and was aiming for >1000 years I would pour the piles to bedrock with stainless rebar inside fly-ash concrete and top those pilings with plate connectors into which you could socket large wooden columns (perhaps 8x8) and build the structure with large wooden members connected with steel connectors and column caps, etc.
I would only use steel members if the span called for wood that was too big (like a 24' span needing a 8x14 or whatever).