I didn't start this until today, so I'm rather behind. Having filled the grid I'm with the negatives on this one. The fact that I've got no interest in the theme is not really an issue in itself; after all, a setter cannot please all of the people all of the time. However, my unfamiliarity with the theme means I'm floundering, and I'm not helped by so much that's vague or cryptic in the preamble. First I'm left wondering whether I've made a mistake in the grid because I have only 2 blank cells to fill, which seems to me less than "a few". I don't know how precise the location of "another small circle" has to be, though I have a rough idea of where it should be. I think I understand the rationale behind the red line to be drawn. But the major obstacle is making any sense of "three thematic markings", especially when doesn't even exist until I have made some changes to an undefined number of letters. I can even see some letter changes in the sw corner of the grid that will yield a word and real crossing words but I cannot see it's relevance. I've spent ages reading stuff on Wikipedia and am still none the wiser.
On the plus side, I did think the clues were rather good.