Roger, your question is a good one, and the guys have certainly provided some great feedback! Here's my 2¢ on what it boils down to:
First, and probably most-important - 250° is the max temp that most consumers will ever use. It's a "safe" temp for the vast majority of home smokers - many of whom don't have any experience smoking meat, until they buy their SI. Along with throttling at 250° to help people not use temps that really aren't appropriate for the majority of smokes, it also prevents wear and tear on the equipment. The experienced enthusiasts can bypass the stock controller, and crank the heat. Steve says the box is rated to 350°. You don't want every new owner cranking it to 350° every time they hit the stall!
Secondly, your question about an analog controller that reaches 350°: I wouldn't think it would be feasible because of the analog temperature swings. Remember, the box is good to 350. Inherently, you are going to have temp swings up to 20-30° above the set point, so the analog controller will take it beyond the safe limits of the box. The Auber can take it to 350°, and NO higher.
Thirdly, what's the real purpose of going higher than 250°? Chicken skin! OK, I get it. But, is that worth sacrificing what I mentioned in the first two points? I wouldn't. Finish on the grill, or the oven, once the smoking is done. Not many folks smoke ribs, butts or briskets at 350°, and that's what most buyers are getting this smoker for.
I believe that Steve, in making a marketing, and liability, decision, has opted for the stock 250° limit because it just makes sense for the vast majority of his consumers. Not many want to push the envelope and break that 250, so it's not worth the time and money to re-tool for the few. Better to have an alternative option for the real enthusiasts who want to break through the ceiling into the higher temps.
When the digital option comes, which is still in the works, it may have the ability to break 250, but that's not decided yet. We'll definitely keep you posted!