316 stainless steel will not rust. 15,000 pound weight bearing capacity per each of 8 vertical stand legs will not fail. The legs and feet are not a problem if you design and construct them properly.
Your underlayment will be your main problem to solve. You have total control over everything but the flooring construction but you may be able to beef it up if you need to, whether you build a steel stand or not. My tank stands on level ceramic tiles laid carefully over a reinforced concrete slab, rated at a static carrying capacity of several times the maximum weight of my fully loaded tank and stand. The dynamic load rating is very high. I don't recall the actual quantitative rating for dynamic loading.
The only metals that do not corrode are gold, platinum, and palldium, stainless steel can and does rust.
http://www.estainlesssteel.com/corrosion.shtml
