We actually do accept requests to take over land and unlock chests if a player has been offline for an extended period of time (generally at least a few months), which are all evaluated on a case-by-case basis.
As for PvP in the world, it's something that we've considered before, including the idea of not having players drop their items on death. Additionally, I've seen in practice that world PvP generally isn't popular in this style of survival server, aside from a few short-lived bursts here and there, and is often only abused to harass players (since there isn't much to be gained with no drops), even with specific rules in place. Ultimately, we're not looking to be like other survival servers, and would rather provide an experience that our community finds enjoyable. It's possible that we would make changes to how PvP works on survival in the future if there is more interest, but most players seem to enjoy the more peaceful style at the moment, as supported by the less than occasional use of the PvP arena.
Hardcore is definitely something we'd like to see more interest in, as we feel that it has the potential to be really fun and enjoyable for those seeking an adventure with more risks involved. I feel that it complements survival quite well by providing a lot of the gameplay points that you mentioned; it's just that there aren't a lot of people interested in the PvP aspect at the moment. We do have additional plans for improving hardcore in the future, so hopefully we can draw more attention to it after we've had a chance to add some cool new features and objectives to it.