if they had gone with 6 films (each book in half part 1 part 2) they could have probably fit everything in

only problem is it would probably take 3 days to watch all the extended editions of the films

films are at a disadvantage when it comes to adapting existing stories because they can only be so long (bring back the intermission i say) and i think that is why in japan in the 90s at least OVAs were so big, you had a story it was too big for a film but probably too small for a TV series (or not enough budget) so they made 3-6 hour long episodes instead