Worf could have been on a mission to protect a colony, the colony sent out a distress call, the Enterprise-E answered, and the old crew together defeated a Founder/Vorta/Jem Hadar squad. It need not have been as intense as First Contact (I agree with Sir Patrick and other cast in saying that First Contact was intense), but with a better initial concept the ninth Trek film could have been a good one.
Personally, I'm of the opinion that Insurrection should have been about the liberation of Betazed from the Dominion and that they'd have borrowed Worf and the Defiant
to help (and maybe even O'Brien). Basically, I'd want to swap the novel 'The Battle For Betazed' for the story of Insurrection. Especially since it'd give TROI a chance to shine. 'Face of the Enemy' showed there were things Troi could do beyond just state the obvious, it'd be nice to see that side of Troi again.