Thanks, Gregoshi, that link is informative - most importantly, it says the campaign lasts 100 turns and so addresses my main concern which was about the length of the campaign. The report emphasises the "blitz" nature of the campaign, but 100 turns is sufficient to motivate me. The multiple stacks I expected - they were part of what made BI fun. It would be good if they sometimes doubled up when attacking you - so they could bring their numbers to bear - but that may be too much to hope for.