Right now it makes no sense whatsoever to defend camps, because they are not defensible, unless you have a blob there accidentally, for obvious reasons. But that doesnt count. You invest into the upgrade, you siege it up, guard it a bit, but have to leave, then a few enemies come and take it without any problems, even if you stay there and call out, it will be 80% times too late for anyone to react. Why? No palisades. Siege is overrun and destroyed instantenously even by a 5 man team.
A palisade upgrade in 3 tiers would be perfect. A wooden log palisade like in the middle ages. It would surround the camp with wooden walls, that unlike fort walls, can be destroyed by normal attacks and take extra damage from siege engines. It should be strong enough to delay small sized teams, make siege inside the camp useful, give time for defenders to react, but it wont really be any issue for a zerg that will take down the walls really fast.
Examples of the upgrade:
Tier1:
Adds wooden walls around the camp. The walls can be passed through, but slow the enemies down to 20% of the speed and apply bleeding. Its like spiked wooden poles in the earth. The thickness of that area could be say 5 meters. You can port past it.
Tier2:
Adds a impassable wooden wall to the existing spiked poles. The wall can be destroyed by normal attacks, each segment has the hp of a normal flame ram. The wall takes extra damage from siege engines. Can hold 5 people off for 2 minutes.
Tier3:
Reinforced walls, more hp, can hold 10 people off for about 2 minutes. Archers added along the wall, that shoot through narrow cut out gaps at whoever is outside while taking 50% damage from attacks being protected by the palisade.
This is badly needed. Anet, please figure out how to add it
Perhaps my version is too OP, but these things can be adjusted as needed. But walls for camps are a must. Otherwise you can as well remove all upgrades from the camps.