I don't think that the grit is that much of a concern… Anything in the 3000 to 6000 grit range will be more than fine for what you need. Most of the stones we are talking about are relatively fast cutting, and I have personally tried jumping from that Shapton 1K to all of them with no trouble. The bigger issue that you have is that the finished consistency that you are looking for is really going to be best with a permanently soaked resinoid based stone. No other stone will provide that same kind of aesthetic finish. You can get close with some, but you will still see streaking around curves. For example, the Gesshin 3K splash-and-go stone leaves a very nice looking finish in terms of how mirrorlike it is, but it will be streaky around curves, as it's a harder stone. Also, it doesn't provide quite as nice of tactile feedback. The 3K soaker and 4K soaker will both provide much better cutting speed and tactile feedback, but the finish is not going to be anything like what you are looking for. The 6000 S provides great tactile feedback and is quite enjoyable to use, but again, the finish is not going to be quite like what you are looking for. Because of your limitations, you will be forced to make some kind of compromise in this regard. You could try using a resinoid based on without soaking, but you just won't be getting the best performance out of it for what you are looking for specifically.
With respect to grit contamination, I think that this is probably an overblown issue. If you are trying to compete in a Kezurokai (wood plane competition) it might be a bit more of a concern. But in the scope of normal sharpening and polishing, as long as you keep things generally clean, you should be fine. I could show you what our setup looks like here in the kind of work that we are able to do with this. I think you would be surprised at how little I worry about grit contamination.