I've abandoned this, having explored all the slack in the instructions that I'm aware of, and having read the whole thread.
Aside from the tenuousness of the solving path to the endgame, and the seemingly wilful withholding of key information by the setter (it seems from some comments above that the instructions were inadequate for any solver who didn't get lucky), I think that the clues (definitions AND wordplay) were pushed too far, the vocabulary was also generally obscure, and there were only six thematic entries in the 13 x 13 grid.
I'm thinking about puzzles where the filling of the grid is an integral part of the endgame - e,g, Sabre is brilliant at that. A good Listener crossword always feels like a, ahem, crossword. However, I endorse the editors' decision to publish it, it's (probably) all part of the fun, and they try not to interfere more than they have to, which is only right.
Looking forward to Friday.