There needs to be some way to destroy walls you own. I really don't care how, so long as it's not something ridiculously time consuming, or requiring 20,000 strength. We took over a village mate's old copper mine with a satelite village recently, and he was wall griefed. There are palisades strewn all around the mine area. We've smashed a clear path around the outside of his original wall and built a brick one, but there's still his original wall inside, which we need to remove for placing smelters, and some hanging out messily outside, which we'd like to remove for space for other things. There's probably 50+ total tiles of palisade. Even with the four of us, all with 100+ strength equipped, using picks and the ram, it takes 2 1/2 - 3 stamina bars per section, and about 15 minutes. Knocking down the 5 we needed to build the brick was fine, and I could see it for a misplaced wall section too. However the constant drying waits, the time taken per wall section, and the player requirement makes it totally infeasible for any sort of large demolition. I should not require a ram, three friends, twenty chests full of tea, or twenty full of food and a nearby river/well, and over 12 hours worth of game time, just to knock down a grief wall some idiot placed there nearly two months ago.
As for authority to revoke, this really isn't a huge issue. The owner of the mine I was speaking of wasn't online when the village claim went down, so we were having to build around his claim. For sake of curiosity I tried revoking it, and it would have cost me over 360,000 authority. New villages cap out at 250k, start much lower than that, and this claim was only like 25x25. If you've got a good sized hermit claim (Somewhere around 60x60 for my old one) they'll require several hundred thousand authority to revoke you.
I say either add the previously mentioned acid, and while it's on the wall section, you can use destroy action on it, and it will take the same period of time to destroy as it did to build, and the same stamina. Alternatively, the no soak on objects owned by the player (except in my opinion you should only be able to do it on your own claim or on land you have vandalism rights to, not on anything unclaimed) is a very nice option, because it'll also allow anybody who has a claim to have mastery over it. You guys go for realism, but how realistic is it to have to build a ram in your own city to knock stuff down? The need for a ram is due to the offensive role they play and the need for them to work quickly. Anybody who lived in the city could dismantle it piece by piece.