And really, it's tailor-made for a feature adaptation. The first installment can use a relative no-name cast; the budget requirements are relatively small; locations are almost entirely remote, forest settings; set requirements are minimal (you need The Princeps Memoriam, a few bedrooms, a Grand Hall for Bernardholdt, and a stereotypical Castle Courtyard for Second Calderon)
There are only a few casting issues. Number one, Tavi is very small for his age until Cursor's Fury and Captain's Fury when he rapidly catches up and fills in. You might need two actors for Tavi. Second, Kitai can be mistaken for a boy when Tavi first meets her, but by Cursor's Fury/Captain's Fury she is described as an exotic beauty. Once again, two actress might be needed, but the same actress could potentially play Kitai and the Vord Queen. Third, there are distinct skin colorations for the different regions. Marat are pale, Countess Amara is described as having golden skin, another region is described as having swarthy skin etc. I personally not be opposed if some of those regional differences are discarded (except perhaps the Marat), but it might upset others.
With regards to Furies of Calderon sets, like Kindler mentioned, they are pretty generic for the most part. Steadholdts are interchangeable, mercenary camp, Marat camp, generic Castle (just have to make sure that this is consistent across all the seasons). The biggest expense will be the Wax forest and the Wax spiders. Even that can be mitigated though by creating one medium set and showing it at different angles to simulate different parts of the forest. The single biggest expense of the first book would be the Marat horde with all their animals.
My biggest fear about a Codex Alera series would be that they would try to save money and cut costs by cutting/limiting the battles. If we are going to get a this series made into a show I want a commitment to show all the battles in all their glory.
One thought I had: if this would get made into a show, maybe they could convince Jim to write a few short stories that flesh out some of the event surrounding First Calderon, the romance between Isana and Septimus, and the death of Septimus. Heck maybe even a little more backstory for Fidelias (what transpired between Academ's and Cursor's Fury) would be welcome. These things are touched on in the book series, but could be slightly expanded and used to pace/fill in the show.