It seems to me you are talking about 2 different things here.
1) you want less clutter and more of a wilderness feel to the game for as long as possible.
The dev's certainly agree with this idea and are redesigning cities to deal with this. This will help a lot. As to the exact role of the outpost, the dev's don't seem to be too certain about this. It would seem to me to be a perfect fit for the outpost to work the way a starbase does in GalCiv and it combines very nicely with the other point of resource efficiency.
Right now all the outpost really does for you is extend your zone of control and provide vision for you. It can in fact backfire against you when you gain the tech to build roads to your outposts because then anyone can use them to run around and tear up your stuff. As well as using them as a homing beacon to find your cities. This would be a real problem if you were not fighting an ai but instead a person. It would be nice if roads were private, and you could make treaties to allow temporary passage through sovereign's domain
2) You want the distance a resource is from your town to have some impact on how effeciently the resource is being harvested.
I like this idea immensely, and you can add in the mechanic from galciv to give your outposts some character. Is it a military fort ? A merchant trading outpost ? perhaps its a magical sentry post. Pariden's monolith spell could have bonuses to its magical effects or have traits that are uniquely available. A more military empire nation could have a unique fort that gives strong military bonuses. This adds depth to the mechanic, adds faction defferention. Gives a reason for CAPITAR to be - which the dev's seem to be at a loss for (think of rome. They built their military, but they didn't enslave you, they wanted an enforced market to sell you their goods, or else) They stole knowledge from others and capitalized on it, making a fortune.
You have a magical way to win the game, a military way to end the game, an adventerous way to end the game. How about a cultural way to win the game using a similar influence mechanic and make that zone of control really work for you ? 4 different game winning strategies, and each faction would have a different means of accomplishing them, some more efficient than others, but all viable.
A cap of some sort on the number of outposts or monolith's you can create is not an arbitrary thing as an outpost is by definition and extension of a city or state. It can exist without it and is there to enforce the will of that state. It makes sense that there should be some limit on how many of these you can build. For example some factions may not be able to build outposts, and having no monolith spell, they have a greater zone of control from their cities since they would be more vigilant about sending out patrols. Others use an outpost to drain an area of resource and then abandon it. This way they have no need to build a city there - they have more of a locust mentality. How a faction wants to enforce it's zone of control says a lot about what that faction is like. To simulate the draining effect that faction could create a temporary outpost that exists for a set number of turns and then dissapears, then they have to wait a period of time before they can build another outpost in that are, leaving it fallow for when they return. This could be a good hit an run mechanic for tarth for example if they field small, efficient armies of 3 units.
There should be a limit on how much you can enforce your will outside of your settlements, and some factions will be better at it than others, some will require it to make up for less efficient structures, and some will have more efficient structures but need for less outpost structures
