Personally, I don't think there's a need to remove Outposts. A Lv 1 Outpost generally takes 30-40 days to break even on resources, scaling up to 60-80 days for a Lv 10 Outpost, so it's understandable that people don't seize them because they can be easily seized by larger players afterwards. But if you think about it, villages suffer from the same issue as well, but there's not much aggression happening on that front in general. If making RoI on Outposts really becomes a major issue, then we can just have it so that Outposts cannot be abandoned nor attacked by another player for 30 days after being seized. That would give the player who took the initiative to attack an Outpost enough time to conjure up enough defenses for it. If anything, I think we should be getting better incentives from attacking Outposts instead. (And yes, this is a biased sentiment coming from someone who holds a few Outposts scattered all over the map.)
Character Name: Rimuru
I had been unconsciously using the cost of a village soldier. Let me work it out....
A level 5 outpost produces 10 of one resource/hour. To produce a Pike or Archer costs 50 gold + 1 of each of the 4 resources. If we assume a price of 3 gold/resource (from my experience in the Market), that's 62 gold to produce one soldier. So the level 5 outpost produces the value of 4 soldiers/day, roughly.
I just ran into a level 5 outpost and the dark wizard has 4,270 archers and pike each on it. So that's 8,540 soldiers needed to sieze a piece of land, for an ROI of 8540/4 = 2,135 days, roughly. Six years. The amount of dark wizard troops scales with the production rate, so it's the same for all outposts.
Oh yeah, I see I do get 8,540 resources if I take this outpost. That's worth 413 soldiers per my math above, so knock about 100 days off my ROI estimate above. Still almost six years. That's just too much by an order of magnitude for a game of this type, IMHO, when the outpost can be seized from you at any time.
Just my 2 satoshis,
EnderWiggin