I checked to see if there was a similar thrad but I couldn't find one. If I missed it please let me know. Some of this discussion will kind of mirror what others have said about city bulding.
There has been a lot of talk about how cities are kind of boring and eed to be imrpoved, I feel the same way about outposts. They just kind of sit there and don't do anything besides expand your border. I think they could be a lot more interesting.
Firstly, there should be several different kinds of outposts. For example, we could have a watch tower outpost with an increased sight range or a redoubt style outpost that adds defensive bonuses to a unit stationed there. There could also be civilian outposts like a hamlet that generates a small amount of gold or a trade outpost that could generate some gold through caravans. By adding in different types it would add a strategic desicion to what type of outpost goes where. Building a redoubt on the only path through the mountains would be a great way to block an enemy. At least until they flatten the mountains with some magic.
Secondly, Outposts should be captureable. Currently they are just annoyances to be rounded up in a war. If they were capturable that would add some strategic desicions. Do you head straight for the cities or take some of the enemies watch towers so you can move through an area unnoticed? This could add another layer to the resource war, instead of just destroying resources around a city, you could take a small forward base to build up for raids/an assault.
To balance this out outposts should have a cost imposed on them. Whether this is an upfront cost or upkeep or maybe both would need to be tested. There would also have to be a way to make sure that players aren't just spamming outposts, especially if they have the abilitiy to supply resources. Maybe make it so that only certain types of outposts can be built near their respective resources.