Hi Capsuleers and CCP,
Because it’s crazy/insane to travel through the universe with a few minutes, I have some suggestion about the structures sharing, it shouldn’t be that easy to travel.
When you see more than 25K toons (not players, I know that) inside an alliance there is something to consider. I love big fights, but I want more contents as well (only me think that ?).
The first part is about contacts.
An alliance can’t add contact at all. So, you can’t share your structures with another alliance.
A corporation who is inside an alliance can’t add contact.
A player has a limit to add contact around 50 and it will be only players or corporations. A player can’t add an alliance in the contact list.
A corporation without an alliance can add players or corporation has a contact.
The second parts are about sovereignty.
An alliance (not a corporation) in null sec should had to declare a headquarter. More the systems are far from the headquarter alliance more the cost it will be to keep the system. When it’s outside the region from the headquarter it will be a hell to keep it.
Inside headquarter system, I think it you should add something that will impact the region. Like if the alliance who has the sovereignty loose some ships it will be bad. If there is no one in the headquarter and an “Enemy” show up, they could mess with something, that will have an impact for the region (production, pve,…).
Have a good day capsuleers and CCP 
Fly safe o7