I have seen the videos where the new cast members are introduced and they say who they will be playing in season 3. I did not see anyone cast as Mace Tyrell, Paxter Redwyne or Mathis Rowan. There has also been no mention of Willas Tyrell or Garlan Tyrell, the only Reach character that was added was Olenna Tyrell.
If there is to be a full small council meeting and there are no Lords from the Reach, will Olenna, Loras and Margeary represent the entire region of the Reach?
This is not a minor deviation from the book. If the power of the Reach is repesented by a widow; a maid and a knight, who is not an heir to anything, it will imply that the Reach is not all that powerful. That would mean that the Lannisters are not dependant on High Garden's power and that changes the arc of the whole story a great deal.
I do not mind some simplfications due to time and budget constraints created by making a TV show but some of these changes are creating a butterfly effect about which GRRM himself warned. I am worriedGame of Thrones will beTrue Blood and will deviate far from the orginal source material. The ASOIAF Books are wonderful and I would hate to see the HBO show, in future seasons, become some ossified, puerile, kitchy faux-medieval comic book, which is where it would go if it is allowed to go the rouTrue Blood..