Ok, first off i'm sorry if this has been mentioned before...i did a quick search and nothing came up apart from the other ideas of fixing hearthvaults.
This is a simple idea, it will not completely fix the hearth vault issue, but mainly the issue of re-oathing to another vault while your vault is under attack.
So here is the situation at the moment: Rangers track to a vault, set up a ram, the raider sees the ram and oaths to another vault and hides in there. What if there was a timer between leaving a village and oathing to another? Rangers track to a vault, set up a ram, raider sees the ram and says "Oh shit! I have to actually break the ram or find another way to get out of here".
My suggestion is the time between leaving a village and oathing to a new one should be longer than the time it takes for a ram to dry. Or even the same time. This would also solve the way people port around to world to allied villages.
This would render trade alts somewhat useless, most people may not like this aspect. But I for one would like to see a trade city like Constantinople rebuilt.