I don't think the order mattered according to Oda. I'm pretty sure he said the divisions weren't based on strength, even though the top divisions were obviously stronger. But Oden didn't become the 1st division commander, and Ace was ahead of Jozu. To me it seemed like the first 4: Marco, Ace, Jozu, Vista were all well above the rest. The rest of the division commanders were probably comparable in strength despite the difference in number.