A more interesting map does sound fun, but it will be sad to see the old map go, with Vivec and stuff. If you do go ahead with the islands make sure there are big enough islands for large cities. Also, I agree that would we shouldn't plan out the city next time, and just let it develop. I know nothing about Bukkit but if the last world was anything to go by we should try to go for as few mods as possible. I don't really see the need for NPCs, chest shops, placing fences on fences and I have no idea what War and nSpleef do. I'd like to see a more vanilla server, with only BB, a creeper nerf and maybe iConomy and the command shop mod (whatever it is that does that).
What would stuff like NPCs and placing fences on fences hurt? We don't even know if mods are causing the corruption.
And I think chest shops would be really useful. I think they could possibly phase out having to use the command shop (which is fairly broken at the moment, considering everything loses it's value eventually since all people do is sell).
Also, I'm pretty sure we're going to try and bring Vivec with us using WorldEdit or something. That would be the only thing we'd bring though. Too much work to lose.