A few things that might be of interest to you.
If you had ever used a view camera, you would know that, shiifting the image was almost always done with the camera back, not the front (as with TSE lenses), because front shifting, even that done in the perfectly parallel way that the TSE operates, in effect, subtly tilts the image plane, so that you must compensate in post if you want to use front shift to stitch two or more images together. Granted, the amount you have to work in post varies and is rarely a huge amount. But, front-shifted images will never stitch properly without some image manipulation. If you use grip equipment to hold the camera and lens in place by grasping the lens, rather than the camera body, then, relative to the image you are shooting, when you shift the TSE lens, you will actually be shifting the body (camera "back"), rather than the lens (camera "front") itself, thereby eliminating the problem and making stitching in post completely idiot-proof. All of this is to say that, if you use the 24mm to stitch two or more images together in place of using the 17mm, you can simulate the 17mm to a degree, but be aware that you may want to buy some exttra grip gear to make that process easier and faster. Furthermore, be aware that, depending on the camera orientation when shifting for stitch, you may reproduce the general angle of view of the 17mm, but not the same format shape. Finally, you can always use the same stitching techniques with the 17mm, so that you could create a still wider angle image that would still not be reproducable with the 24mm using the same technique. Taking all of this into account, the 17mm is a better choice if you often need a lens wider than 24mm for your work.
As to filtering the lenses, of course the 24mm is the obvious choice. For very long exposures with the 17mm, if only the effect of graduated ND's is required, one can use a black card to variably dodge a lighter portion of the top of the image area, by rapidly waving the card in and out of the optical path of the lens in front of the camera. This technique requires practice, but works just fine, if the exposure is at least a few seconds long. The same technique, but using one or more stationary black cards or manufactured cloth gobos (flags, fingers dots, etc.) mounted on stands in front of the camera, can be used to cut off light which would otherwise shine directly on the lens, thereby taking the place of a really good lens shade. For other filtering uses, expensive large and cumbersome adapters are, or will be, availbale for the 17mm, but the cost, and the cost of the then necessary very large filters, will be very high.
Good luck and happy shooting.