As a Canon DSLR user, there are two reasons I'd sell my gear and move to Pentax: budget-conscious weather-resistant lenses and super-small primes. But neither has the bodies to take full advantage of them, i.e., an entry-level body with weather-sealing or a low-profile DSLR body.
There was the K-200D, a weathersealed consumer-grade body. But when it was available, there were no consumer-grade weathersealed lenses. It didn't sell well at the time, but today used copies sell for a lot for their age because people want the smallest, lightest weathersealed body they can find, and now there are small, light, inexpensive weathersealed lenses to put on it.
But the K-200D was not that much smaller than the K-7 & K-5. To get an idea of the least amount of size and weight ever added by thorough weathersealing, compare the K-200D to the K-100D. A weathersealed K-r might be a bit smaller than the K-200D, but still noticeably bigger than a K-r.
I do think they should have a consumer-grade weathersealed body -- basically a weathersealed K-r. I think they're walking away from a lot of sales by not having one (now that they have consumer-grade weathersealed lenses to go with it).
If Pentax had a K-r body with weather-sealing, they could market it to every photographer who wants to hike and take pictures in inclement weather but doesn't want to pay pro-level costs (Canon L lenses or K-5 body) and wants to travel light.
Many people who want that eventually go with a used K-200D.
And if Pentax had a DSLR that looked more like the old K-1000 or were even more radical and had a rangefinder body like the Fuji X100, they could attract a ton of photographers who want the low-profile, street-shooter package.
The K-1000 was not a compact camera. You might be thinking of the ME, MX, etc.
A tiny prime on a K-5 body just looks weird, but if you could lose the grip and streamline the rest, you might have something interesting.
I guess it depends on whether you consider a camera a tool to use, or a work of industrial art to look at.
Rescue Pentax from what? Even Thom Hogan hasn't predicted Pentax's demise in over a year. And he LOVES to predict Pentax's demise.
Greg
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Brand loyalty is a character flaw.