Problem 1) Outside of JH there is not a lot for an established guild to do. Established guilds need more JH.
Problem 2) New guilds are very vulnerable during JH and having some days off to build up and prepare is fairly mandatory to have a chance to get a foothold.

Proposal:
JH is 2 hours per night, every night at the same time but your guild's land claim may not be included, based on its rank.

Rank 1-3: No exclusions (7 nights a week of JH)
Rank 4-6: Excluded Monday-Wednesday (4 nights a week of JH)
Rank 7-9: Excluded Sunday-Thursday (2 nights a week of JH)
Rank 10: Excluded every night except Saturday.

"Excluded" means your realm claim and town claim are safe, as if JH did not exist, but you can still attack others (and, of course, be killed personally).

My breakdown is an off-the-cuff example. Maybe there should be more tiers? Maybe the days should be 7/5/3/2? We can quibble. But you get the idea.

Additionally:
Outposts are always vulnerable during JH regardless of the rank of the owning guild.

Pondering how this could be used/abused/exploited:
You purposefully create small guilds to hide stuff in. But they are still vulnerable 1-2 nights a week and you can't hide much stuff without bumping up the rank.
???

This gives big guilds a lot to worry about and a lot to do.

It lets new guilds (or badly beaten or abandoned large guilds) have a breather but never gives anyone total invulnerability.

Your rank 10 apple tree farm can still be chopped down, just on Saturday. And if you actually put up walls or store apples you'll probably end up bumping your rank up for increased vulnerability.