You mean introduce a new range of lenses with a new mount and shorter registration distance? A mirrorless K-mount FF won’t be smaller than a DSLR, courtesy of physics/optics.
It would indeed be lighter, and simpler to manufacture and repair. However, as I’ve written here before:
DSLR: Most of the camera’s electronics remain in standby most of the time. At those times when you’re not actually taking a photo, the only electronics in use are the exposure metering sensor, the AF sensor, and the AF motor.
Include the LCD too if you’re browsing photos, or you leave it on by default, but that’s the user’s choice.
Mirrorless: Everything is live all of the time. In addition to the three listed above—exposure metering, AF sensor, AF motor— you are also powering the main sensor, image processor, and the LCD/EVF, whichever you use to compose.
Many people will cite greatly reduced battery life as a result of this, but others counter that you can always bring more batteries.
(cont.)
Started out doing photography at the age of 6 using an uncle's old 1940 kodak brownie box camera. At 15 years of age, I decided to buy my very own 1975 Praktica SLR camera. I now shoot with a Nikon D850. I do unpaid TFP and commercial paid work.