Also, if you've forgotten the text string that has to be used in the query, it would be neat to have that text string included somewhere (as a reminder).
Is the suggestion here about giving a reminder as to what the syntax is for using the plugin?
Although I may be mistaken, I have this vague memory that there might be some upcoming changes to FARR that make it easier to get help on the currently functioning plugin. I'm thinking that may be I can leverage those when they come about. I agree it would be good to quickly find out what the syntax is -- I just don't currently have what I consider a good way to achieve this. The key is the word "somewhere" in the original suggestion
Yes, I don't disagree with you at all (in general I would have thought that the results url would not be part of the OS definition, and so couldn't be incorporated in your Plugin [a guess])
I may be mistaken about this, but I was under the impression that the specification provides something along these lines, but it is optional (I believe there is something about RSS and something about Atom for returning results).
I'd think that if a site provides an xml view of a search result then that is not scraping their results at all. But I'm not certain and happy to be corrected
It has been a while since I checked, but IIRC in Google's case there was quite a bit on this  -- including having a "key" to make use of their XML results.
I didn't mention another potential technical issue -- in theory it sounds neat to be able to work w/ results inside FARR, in practice though, imagine what happens after you request that a search is performed. You end up waiting -- and while you are waiting, if FARR is involved, it makes it difficult to use FARR for something else (as I understand it, FARR isn't designed to work on multiple tasks simultaneously, especially if they all involve the FARR window). I think letting a web browser handle the request works out ok for the most part -- I usually want to view the individual result pages in a web browser (perhaps I am missing use cases you have in mind -- would you mind elaborating a bit on this point?). Also, it's harder to revisit the lists of results from inside FARR whereas w/ a web browser I find this is much easier (especially w/ tabs and opening recently closed ones).