Do you think this should be continued/remade as a longer series?
The worst thing for me about BS6 is the fact that it's only four damn episodes long! The characters all certainly made an impression on me, but I really think that both they and the show itself could be even better if it was longer - say, around 26 episodes or so. I'd certainly like to see more development of the relationship between Verg and Zorndyke, and also more development of the characters of the Blue Sub crew, most notably Kino, Iga and Huang.
More than anything else though, I'd REALLY want to see a much stronger emphasis on the relationship between Hayami and Mutio. For me, the meeting between them in "Hearts" really comprised the core of what the entire series was about, and there just wasn't enough of it.
Well, we can always hope, I suppose. If any Japanese series needed a longer and more fully developed anime, "Blue Submarine No. 6" is it!