The major issue in attaining a bigger viewfinder image is not the eyepiece magnification (that can be solved with the addition of an external magnifier) it's the autofocus system that channels a significant portion of the light away from the focussing screen, thus making the resultant screen image dimmer. The laws of physics govern the amount of light left for the eyepiece, so the only way you'll achieve what some people are asking for is for the manufacturer to supply a camera that is strictly manual focus.
Good luck with selling that at an acceptable price and making a profit from it.
I sympathise with the notion of an eyepiece image that is akin to film SLRs. My first SLR was in the early 1970s and was a Pentax S3. I still have a SP-F, a K2DMD and an LX, so I know what a good viewfinder image looks like, too.
The simple fact of the matter is that the vast majority of the market for a modern DSLR doesn't share that experience, and wants a good autofocus camera, so the rest of us just have to make do with what's on offer.
Given that the K-1 is available at such a reasonable price, however, I suggest that people who were willing to pay more and want a dedicated MF Pentax DSLR can think about customising a K-1 by replacing the mirror with one from a film SLR and likewise with the focussing screen. Obviously, that will require a technician's skill set to undertake, as they're not intended to be replaced, but they were assembled by human beings, so it should be achievable, if that is your essential requirement. I imagine that a good technician could do what you want in no more than two days of work. At $80 per hour, that makes the cost of labour less than $1,300. Of course, you'll have to find a compatible mirror and focussing screen (thickness will be the main parameter involved, as older SLRs will have bigger mirrors and screens that can be cut down) so that's a threshold issue. Of course, you'll lose warranty in the process, so you'll have to factor that into your thinking. You'll also lose focus confirmation, as well.
If I really wanted a dedicated MF Pentax DSLR, I'd seriously consider doing that, but I don't, so I'll take what Ricoh is serving up to me. The K-1 will have a slightly bigger and much brighter vewfinder image than the K-3, so I reckon I'll be happy using my MF lenses on that, especially the A50/1.2.