Do I need a gear lower than 1:1?
I'd say generally yes. There aren't really any strict thresholds, and you may survive with a 30/25; but in high altitude with a load you'll find that that ridiculously low gear wasn't really as low as you thought. The difference between a 28-tooth and a 32-tooth, percentagewise, is like the difference between a 7% grade and an 8% grade-- pretty minimal difference. To get the closer spacing between gears though, you might be able to start with something bigger at the small end, like a 13 or 14 or even 15-tooth, maybe a 15-16-17-18-19-21-24-28-32 in a 9-speed, if you can get Harris Cyclery or someone else to build it up for you, or maybe the 14-15-17-19-21-24-27-30-34 they have at http://www.sheldonbrown.com/harris/k7.html
I built up a really nice tourer at age 17 (in 1977) when I worked at a bike shop, and my boss had ridden accross the country the year before. I asked him, "How low of a gear would you have liked to have?" (Your "1:1" is a 27-inch gear and I was thinking of a 24.) He said, "There were times I could have used a two
!"-- an exaggeration, but the point was that there was no such thing as too low of a gear for some situations. When you get down to about 16" (20/34), you might think walking is just as fast, but it would wear out your cleats, or be too slippery for walking on such a slope, or just not be as efficient.