Well, I know that Forbidden Lands already has a set of rules for base-building, so I assume there's a nice head-start there. I haven't read them but between that and the hex-crawl I've always figured Twilight was in pretty good hands. But for extended task resolution, like the bridge example, again I refer to Mouse Guard as kind of my personal gold standard for rules that handle that sort of thing well, and make it nearly as dramatic and interesting as combat. You could spend 3 or 4 whole adventures on getting this bridge built, and then at the end of it there's a good amount of tension as you find out if it was all for nothing. Then the players are invested in something; if someone comes and tries to blow up that bridge, you can bet it's gonna be more of a grudge match. It's a great idea for a slice of a campaign. I hope the rules provide a number of resources like that; other ideas for what players can be doing other than surviving, traveling, and fighting what is otherwise a pretty pointless war.