Cheers for that.

You have been catered for by Pentax for longer than most of us:

You can easily check that by taking an image and uploading it to:
https://www.camerashuttercount.com/
If you're not sure about it have a read of this:
http://www.howtogeek.com/218244/how-to-check-a-dslrs-shutter-count-and-why-you-s...

Well that's more pro's than con's. Got to be good!
Also, "Raw image quality that is among the best the APS-C sensor size has to offer...... the K-70 trumps both its mirrorless and its DSLR competion." Sounds good too, and that's from DPR who are notorious for knocking the brand.
The review also hints the camera's autofocus works better with the new PLM lenses. Oh, and they gave it a silver award!

Yep, never been keen on Marmite sandwiches, yet my old friend at school relished them.
Perhaps you have to like Marmite to appreciate I C M (I C M = Intentional Camera Marmite?)
I'm not intending to sound rude, but I've had colour slides coming out like that and the best use I could find for them was to save the mount for something else! I'm positive had I entered any in a club photographic competition it would have been first to go with the comment, "Nothing's sharp, why did you enter it?"
Maybe times have changed but you can't unlearn the knowledge you picked up in the past. I can see the value of a blurry movement picture in a story sequence where perhaps a fugitive is running through the woods to escape capture, but not as a stand alone image.
I can also appreciate movement of trees in a photo may give the impression of a windy day, but at least the background and forest floor would have to be sharp. That might require combining several images to achieve. But a pure blurry photo just looks like it had the wrong exposure (I've had many of those) or the photo took itself accidentally between other intended shots (I can do that too) but I wouldn't normally like to embarrass myself publishing them to the world, other than to show things to avoid in a camera demonstration.
To me I C M is when one would do a panning shot of, say, a vehicle which itself may not be perfectly sharp if it was a slowish exposure but would have a definite blurry background. The blurriness tells the story of the vehicle speed. Another might be to zoom in on a vehicle coming towards you which achieves a similar, although different, result.
If I hadn't come from the 'old school' which says 'something has to be sharp in a photo' how would you sell me the idea of this new approach to I C M? I'm presuming this is now taught in art schools, or is it purely experimental?
Thanks for hearing me out.

Don't get it. Can someone explain please?

Internal lens reflections.

It depends on the DA lenses you have (we've been here before!) Some DAs are compatible in varying degrees (but some aren't.) You may well be able to use your DAs in FF mode but I've said that without knowing which you have so can only say that in general terms.
The K-1 has nowhere near the image noise of the K3 variants and as regards APS-C mode will be closest to the K5iis. Some regard the IQ of the K-3 variants as being inferior to the K-5iis (but I'm not in that camp myself and still use my K-3 on occasion.)
Getting FF lenses would make sense in the longer term if you get a K-1, but you may not need or even want to ditch your DAs. Some DAs are FF in disguise!

Well there's no AA filter, so not quite the same as a K5ii and the dynamic range is slightly higher on a K-1, but only marginally so there are differences. Why not compare the images at http://www.imaging-resource.com/PRODS/pentax-k1/pentax-k1-image-quality.htm and http://www.imaging-resource.com/PRODS/pentax-k5-ii/pentax-k5-iiA7.HTM because you know what you're looking for?
Often the ultimate IQ depends on the processing of the image and your work flow to achieve that. Given the same lens on either body I would say the final images should be close but with slightly better definition from the K-1 due to lack of the AA filter. They won't be the same because they use different sensors, but certainly similar as both come from the same stable.

Any DA lens will work on the K-1 the same as on a K5iis at the same resolution and will, by default, use them as APS-C lenses. However many DA lenses cover a larger area than an APS-C sensor and the K-1 can be made to over-ride the default APS-C setting and use them at either full frame or 1:1. Some DAs are completely acceptable at full frame, and some with only marginal loss of definition and/or vignetting, Two of Pentax's cheapest lenses, the DA35mm f2.4 AL and DA50mm f1.8 perform particularly well in full frame mode being based on earlier 35mm film lens designs.
If you indicate which lenses you are concerned about I'm sure someone will have tried them by now and report about their level of compatibility if that might be of interest.