Okay - I'll take a shot at this.
[tl;dr: with @rhetorician, I believe "sit" in Rev 17:1 is intended to convey the settledness of a potentate in pomp. This sitting/setting needs to be seen in the immediate context, and in relation to John's use of the Hebrew scriptures.]
This is "Biblical Hermeneutics.SE", though, so I'll start with two general principles for interpreting the book of Revelation (the two most helpful for this question; there are others, of course!), then proceed to apply them to Rev. 17:1, and draw out the nuance that, to my mind, best suits the verse.
That's my take anyway, for what it's worth...
G. R. Beasley-Murray, The Book of Revelation (New Century Bible; London: Marshall, Morgan & Scott, 1978).