I only recently finished the game, and really enjoyed it.  Definitely one of my favourite FPS games in recent years.  I didn't really have an issue with the outposts not resetting, because it helped to make you feel that you were making progress to claim the islands back - and as I kept switching between story missions and exploration, I was encountering pirates etc., all the way through.  So resetting the outposts is something I personally would not use.

However, I think the things that made the game a bit too easy (for me) were (1) unlocking free weapons by claiming back the radio towers, and (2) the sheer profileration of loot/cash lying around.  I never once ran out of money - and actually got to the point where I was simply buying everything, including maps, just to get rid of all the cash I was carrying, and simply discarding half the items in my rucksack.  The game would have been much improved if access to better weapons was a lot harder, and you still had to purchase them after unlocking them.  That would have then required saving up to get a particular gun that caught your eye.

On reflection, if I went back and played the game now, I would not bother with much of the crafting, particularly for ammo/munitions pouches or increasing the number of weapons you can carry.  Personally I would opt for a more restrictive inventory, which I feel would help to make the combat more intense as you would have to conserve ammo, etc. while exploring and during combat.

The other thing I would have liked to see, though, was some kind of tougher commander figure in charge of each outpost.

I do hope the higher difficulty level they are introducing doesn't just turn enemies into bullet-sponges. :/