Many years ago Olympus produced two shift lenses for the OM1, these being a 35mm and 24mm. Unfortunately, the more 'useful' one (24mm) is collectable and expensive! However, it looks like a solution to the lack of a PC lens for these formats, could well be Laowa's 15mm FF wide angle which has a shift function built into it, once a suitable adaptor is used between the lens and the body. Below are links to 2 of the reviews I've encountered: Venus Optics Introduces Laowa 15mm f/4 Wide-Angle Macro Lens Wide Angle Macro Fun With The Laowa 15mm Lens Since this lens is designed to cover the FF 35mm film format, the odds are that any of the failings which this lens exhibits (Shading and fringing) at the edge of the frame, are less likely to be present and of course, being 15mm, this is wider than the versions Olympus originally sold. I've heard of Shift as well as Tilt & Shift adaptors being made in China, BUT it seems these also come with unwanted compromises.
This is exactly the lens I was going to suggest; I'd love to see how it performs on a m43 camera, and how sharp it would be for landscapes at 30mm equivellant.
If you want wider, you might try the Samyang 14/2.8 (it's been available for a while) with the Kipon shift adapter. The Samyang is a solid lens, and I've had good experiences with Kipon (though not specifically with their shift adapter).
