@Vegard:
Erm… The Warship Island-arc is 7 and a half episode long, and there is some manga content mixed into it as well. That's only a little over half the volume. Although I think they should go with 12 episodes for the next four volumes, so volume 5 will end at episode 61, which is the logical ending-point of "Season One". (The journey over Reverse Mountain. Then they should do four 14-episode sets in Season Two to make up for it, so that set 10 ends at episode 130, which is pretty much the undeniable end of the Alabasta-arc... Then we get volume 11, which will inevitably contain nothing but fillers. Argh, buying that is gonna be a pain, yet I don't want to have a hole in my collection either...
I'm just not a fan of the filler arcs, thats all. I don't enjoy paying 30+ dollars (whatever price you find it at) for a "little over half the volume" of filler (i know about the manga related material.. the only filler part I like in the arc takes place when they are entering the grand line.. Nami Pushes Erik, a devil fruit user, into the sea in cold blood. Best death in the series, thanks for the memories Erik).
Plus waiting 3+ months for it non the less.. although Laboon arc is worth it.
I think your idea would make sense when it comes to evening out the arcs in terms of sets. (The Lougetown arc getting it's last episode chopped of and put on the next set would be such bullshit). But I still advocate more Eps pers set