Currently in my PhotoShop (CS6/WIN10/64Bit) I can’t access any Nik plug-ins for files that are typed as grayscale mode.
Although monochrome files don’t need anywhere close to the number of controls that color files do, I find some controls – such as structure – really help when I’m working with scanned monochrome files. A monochrome plugin might look like a slimmed-down combination of Silver Efex and Viveveza, with some pre-configured templates.
There is a small, but enthusiastic and growing, set of analog photographers out there and some of them are using B&W emulsions – often developing the film at home. This includes 120 shooters using vintage and pinhole cameras. They are often new to B&W processing, so a tool set that helps with common problems (negatives too thin, negatives too dense, contrast too high, contrast too low, dealing with grain, scanner limitations, etc.) would be a big help.
I recommend to use color settings even when you copy b/w material.
Many applications have their problems with grayscale mode. Scanning in RGB eliminates these completely and all the known tools should work as expected. For best results, use 16 bit TIFF from the scanner or RAW format files from your camera…
The lowest color setting I have on my scanner is 24bit RGB. Although drive storage is not a problem, a 24bit RGB scan produces a file that takes up a lot more headroom than the scanners 16 bit grayscale setting.
The issue is not to find a workaround. The issue is to have a set of mono-chrome only tools, with a lower overhead, for use in a monochrome to monochrome workflow.
I was unaware of problems with PhotoShop handling monochrome image files.
About filesize: 24 bits take more space than images taken at lower bit depth, sure. As a starting point, more bits give a wider range for treatment without posterisation. You can always reduce bit depth, once all the light related adjustments are done. Pkay, this is an additional step but it might be worth wile.
The issue is not to find a workaround. Photoshop does not require any plugins. The plugins are containers of structured instructions and interfaces that streamline the use of capabilities that exist within the host software.