Michael, I know what you are refering to and DON'T EVEN THINK ABOUT IT! Jay, alternating tread stairs are ones with three stringers and treads on every other side so you can go up or down with half the risers. The problem is that there are building code in this country that apply everywhere. You have to build per code, or get specific approval for non-code items and this is unlikely to happen. They are great for ships, lighthouses and even rarely used areas but patently unsafe for everywhere else.
You might not have young kids that would love to play on stairs like these but the next owners or visitors to your place might and if a kid gets hurt playing on stairs like these, you would be sued big time and so would the building comission that let you put them in. It would be even worse on a deck. Yes, decks have to meet code too. And they are outside so easily visible and you would not get away with having them for long. They would constitute an "attractive nuisence", like a swimming pool. Pools have to be fenced because kids find them attractive and may not be able to read. They fall in your pool and drown and you are liable. If they don't meet the building code, you insurance carrier will not cover you. Same deal on the stairs.