Thanks to everyone who responded thus far. I really appreciate your views and input
By way of further explanation, and to address one of the more common points raised in the responses, I have been shooting only raw for five or six years now, and for most of my day-to-day photography I wouldn't want to use anything else. I'm not intending to shoot B&W JPEG only in the long term... that's not even a consideration.
My interest in conducting this little experiment lies primarily, I think, in the discipline it'll require... greater awareness of light and shadow with respect to composition of B&W images; the need for accurate exposure to avoid losing important shadow or highlight detail (and deciding when and where I'm happy to compromise one or the other); restricting myself to in-camera results rather than post-processing... essentially, working within unfamiliar limitations and outside my comfort zone. I love the flexibility of raw files, but at times I think I allow myself to become complacent or lazy, given the latitude for correction in post
Working with restrictions isn't new to me... I do it frequently, choosing my older cameras and lenses instead of my K-3 and DA Limited glass, for instance; but this would be an entirely different set of restrictions than I've shot with before.
I'm not so concerned about achieving optimum image quality, nor even the nicest possible B&W "look". Of course, I'd intend to set the camera up as best I can for appealing output to suit a range of uses (this, in itself, would be an interesting challenge), and would allow myself the flexibility to choose different filter colours in the settings appropriate to given scenarios... much as any B&W film photographer would choose an appropriate filter in the field. I don't mind that I could achieve much more nuanced tones if shooting raw and converting to B&W in post. This isn't about getting "ideal" B&W photos, I think, but working with whatever I've got available in-camera, free of post-processing "responsibilities"... for a while, at least.
If I carry through with this (and I'm not completely decided yet), I think I
must choose JPEG only rather than raw + JPEG. There's a chance I'd regret it, but that in itself would be a valid outcome from the experiment. If I shoot raw+, I have a feeling I'd be tempted to try processing the raws to see how much better (or at least "different") they would be.
Thanks again for your feedback. If I go ahead with this (and I suspect I will), I'll endeavour to update you