I think I actually wouldn't like to watch a modern movie based on the Kyrou Anabasis. The real advantage and benefit of the book is that it gives a lot of informations about the peoples involved, the kind of fighting, customs and a lot of hints to human behaviour, sometimes not in favour of the Greek soldiers involved. I fear it's impossible to show the real value of the book in a commercial movie. There are no villains and no heroes (except perhaps Xenophon, but ok, it is his book...), so it may be difficult to understand by many. It would even be impossible to accept for many that Xenophon was not the leader of the soldiers, but only one of 10 strategoi and not the most important one. The story in itself is, I dare to say, rather boring, a group of people trying to march through a partly hostile country. Good opportunity to pack the movie with slow motion fighting szenes however... You see, I'm not very impressed by modern movies.
That said, of course I would watch the movie and buy a copy.