I think this game is lacking options to opt-out from PVP by using some defense mechanics that will allow to defend yourself without taking part in combat itself.
You, of course, can sit in your walls, but roaming and interception by offensive party could make game experience of a solo player unbearable.
Akin torches and braziers from salem, which slowly sucked black bile of the intruder, there should be some mechanics that being properly set up and maintained will make presence of unwanted visitors cost more than just time.
Currently there is a single tool that could be used in that way - catapult, but it's rather impossible to use for defense against players.
I won't define how exactly should it implemented and balanced, I just want to highlight main points:
- stationary
- active claim is required
- requires to be set some time before being used
- consumes resources for maintenance
- consumes resources acting
Of course, any measure must have counter measure, the sole intention of the idea is not to make player totally unreliable defense-wise in case he does not have armor, top stats, 4 hours of free time to run and troll belt full of waterskins.