I assume that you have some considerations why the following option isn’t optimal either… but since you haven’t mentioned it and you are asking for ideas, I want to mention that I had a goal to this end at some point which was a continuously running odometer goal, where I would reset odometer between books. Way back when, I came up with an idea how to enter the data if the actual text in a book starts not on page 1 (e.g. preface to skip). So this removes the annoyance to set up individual goals for each book.
I haven’t tried this integration myself, so I am wondering how it works. Do you mean you need to ratchet after a longer book because the pages are posted only on the day when you are finished and you get a large buffer after that? Is it also like that if you “track progress” daily (or every day when you do read) in the “currently reading” list? Because as far as storygraph’s own stats graphs are concerned, pages are shown on correct days if progress is tracked daily, but I am not sure if that’s also what they send through integration. But maybe it’s also too much friction to enter the progress there daily. (I sometimes find that overwhelming, especially since I am also using goodreads simultaneously and track everything in both places + copy reviews to a stand-alone blog).