I would start with the gear you already have, in monochrome mode. With that out of the way, get a range of filters to put in front of it to give you options tha

I would start with the gear you already have, in monochrome mode. With that out of the way, get a range of filters to put in front of it to give you options that can't be done in post processing like pushing the sky dark, etc. There may be some very narrow band filters that prove quite empowering. Also consider that if you have a narrowband filter in front of an existing Bayer filter, you've essentially got an HDR sensor, as the sensitivity of the RGB pixels will have a fixed ratio at that wavelength. You could thus trade a bit of spatial resolution for dynamic range.