Will these things require fuel? Or only certain sizes?

This is a very important question.

Is the only option with new structures going to scorched earth or will there be a way to take over existing structures?

I hate to picture what would of happened to a group like BRAVE moving into Catch that had been completely levelled. How many alliances have truly built all of their infrastructure themselves ?

What makes you think you will be able to take them down after a war is declared in highsec? My guess is that this loophole will be closed and you will have to defend these structures from attackers if you want to keep them. That is a much better design to stimulate conflict and facilitate sandbox play rather than continuing to allow corps to evade conflict by just taking down the structure.

But in highsec and elsewhere, they will not "go poof any day". They will be protected by a vulnerability window for most of the day, and require multiple reinforcements giving you plenty of time to show up and defend. And even if you still can't for some reason, it seems that all (or perhaps most) of your stuff will be retrievable, meaning you are only out the cost of the structure.

If you can't manage that, then stick to the still-available NPC structures where you don't have to worry about defending at all.

Refunding ISK would actually be worse than refunding minerals, refunding minerals would just move allready existing
ISK around while refunding isk would create huge amounts of ISK out of thin air.

Slightly better(but not good) would be to have some kind of intermediary bilding block that each fo the old structures
can be decomissioned into, then you build whatever new structures you want/need out of those, this would of course
lead to large stockpiles of said components so that market would take a long time to balance out.

Also you still have the issue of non-standard towers/items returning less than their perceived value but that will
probably never have a solutionthat that satisfies everyone.

The entosis link solves this problem. Undefended structures are extremely vulnerable, so much so that a single person can take one down if it is undefended with only a minor grind. In fact, it seems like there will be no automated defenses at all, just a vulnerability window.

The days of plopping down a tower and relying on its massive EHP to protect it are over.

However, like the vulnerability window in nullsec, perhaps the citadel could have a scaling window based on occupancy. For example, in a occupied structure the window could be 2 (or 4, or whatever) hours a day, but this could gradually increase the less the structure is used. Or maybe, if no one has docked in the structure for 30 (or 90, or whatever) days, it could lose the protection of the vulnerability window and be open to attack by anyone, at anytime.

Doesn't really matter what the vulnerability window is, the structure needs to defend itself on AI, because expecting people to log on at a very specific time just to babysit their structure 'in case' is a step back to the old days of alarm clock skill queues. As well as a step back from our current POS which do have AI defence (Though it's much better when player targeted).

People should be free to play as and when suits them. Not on a strict schedule.

Indeed. If you remove loot drops and allow them to be taken down after a war is declared there is no reason left to attack them. You would not be able to attack them for profit, and allowing a corp to evade a war by taking down the structure means you cannot even use them to force a fight.

The fact that they can be placed anywhere even removes the niche conflict they might drive over limited/valuable moons.

What is the point of adding something to the sandbox that other players can only interact with by shooting a entosis beam at for no reason or reward? I mean it is nice they are easier to destroy if left undefended than the current POSes, but why would anyone bother spending the time in the first place attacking them?

This isn't going to drive much, if any, player-driven conflict if added this way. They need to drop something, even if it is just some valuable fittings, and removing them should not be an option in the case of a war. Or at least the attackers should get a chance at one vulnerability window to reinforce the structure before it can be taken down so that users of this structure actually have to show up to at least one fight.

Or better yet, remove CONCORD protection from them completely like the other small deployables so that wardecs are not necessary. Attackers would just go suspect. That would drive more player conflict and get us closer to CCP Seagull's vision where everything is destroyable.

... If you want automated defenses, state your case in the appropriate thread.

Each class of structure (ie Citadel, Drilling Platform, Observatory) will belong to an NPC corporation which technically belong to a faction, but you wont see the usual Amarr, Minmatar, Caldari, Gallente stylings. We are creating a new style for each which more accurately reflects their purpose.

With that said, we are leaving the option open to have variations within each class + size, but only where we think we can give them meaningful bonuses.

Edit: I listed Gallente last :tinfoil: