I have been wanting something like this for ages (wide angle converter that's behind the lens)

ET2 wrote:

As I said, an adapter adds thickness. You can't start with the K-mount, add an adapter, and keep it K-mount. The initial mount needs to be shorter so once you add the adapter, the final mount matches the K-mount.

That's yet another flaw of the K-mount mirrorless. We knew it was less flexible in accepting manual focus lenses (no option to attach any range finder lenses,. no option to adapt Canon lenses, etc), and now here is another flaw. No 'Speed Booster' adapter cam be made for it.