Health Savings Accounts Part 1 - Catastrophic Insurance Premiums

So I've been doing a bunch of thinking about  Health Savings Accounts (HSAs) lately. I think that the idea has a lot of promise, but I have a few sticky questions that I'd like to hear some thoughts on.

Firstly, it's pretty well recognized that for any HSA plan to take hold as the primary source of day-to-day payments, we have to have a high-deductible (let's call it $5,000) "Catastrophic" insurance policy to cover incidents and conditions that the average American would never be able to cover through savings alone. It occurred to me that a key statistic regarding the feasibility of this policy is the percent of current healthcare spending that is on conditions that cost more than $5,000 to treat.

Even if an individual's chance of making a claim in any given year is very low, if the bulk of spending on everything from open heart surgery, to cholesterol treatments, to chemotherapy regimens, to kidney dialysis, to helicopter lifts from accident scenes takes the lion's share of the total health care bill, then will the catastrophic premiums be sufficiently low to encourage people to opt into an HSA system where their insurance premiums are only marginally lower, but their day to day expenses are now paid out of pocket?

OK, that's the first sticky question, but I promised to keep my posts short, so I'll end it here.
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BTW, here is the long Atlantic article that sparked my curiosity in the subject.