So, I tried searching but couldn't really find anything similar, apart from the old complete development list:
"Core29, EXTERNAL CONSTRUCTIONS, (Future): World map roads, bridges, walls and tunnels shouldn't just be products of world generation. You should be able to dispatch dwarves and materials to accomplish these tasks (though the amount of material used in a typical world generation road would virtually prohibit doing this as it currently stands, so something has to change)."
Anyhow, since toady is going to "Replace dwarf mode generated caravans with actual caravans" moving across the map to your fortress, I was thinking that it's about time we should have some ability to connect our fortress to the world-map roads or at least our mountainhome if none are constructed. Hence some discussion as to how this would easiest be achieved might be useful? ^^
With hilldwarves also coming into play soon I thought they would be the natural option to use as labor. That way we wouldn't have to sacrifice our own valuable workers to do it or have an as complicated system for workers moving off the map to work and then back. In exchange we'd have to provide the hill-dwarves with some suitable amount of food for the workers or maybe goods/coin if the economy comes back before this.
You'd start with having constructing a road yourself up to the map edge, after which the dwarven liasion would give an option to "order the hilldwarves to construct a road". Then you'd get to choose the material, the simplest being a dirt road ofc which wouldn't need any additional materials to construct, just the labor. You could also order a paved road (or if implemented a gravel road), these requiring you to gather the necessary materials and send off in wagons, which would also provide an excellent way of getting rid of all that excess stone lying around.
Some calculation would then be made for the distance and path the road would take to connect to the nearest site/road, an estimate of the materials required if a paved road was ordered and an estimate of the time it will take to finish. This could also be influenced on the amount of hilldwarves in the area and how much you are willing to pay for the work. Having a functioning road would then unlock other civs to send actual wagons, whereas otherwise only pack animals could reach the site. Building a better road would allow larger caravans and be seen as a step towards becoming a mountainhome (the old "road value" required would also now include actual connectedness to the rest of the kingdom).
Also to tie in with the upcoming army arc features, if at war some measure of defense for the construction might be needed. Otherwise you might end up getting word from the liaison that the construction workers were killed/driven off which would alt the progress of the road construction until you could gather new workers as well as guarantee their protection.
Lets brainstorm a bit and see what we can come up with to help flesh this out shall we? ^^