While I am whole-heartedly in favor of fixing the mess that POSes are in today's EVE online, there are some serious concerns with the new structure mechanics as they relate to wormhole space. Some of the points made here have been clarified in the comments by CCP which I have included. Jump to the end for the TL;DR version.
1. Citadel structures, while equipped with defenses, do not auto-defend themselves
This is a problem for wormhole space specifically though I believe it extends to any and all structures in all areas of space. If you require a person to sit at the structure during the vulnerability window, that is doing the opposite of encouraging interaction. In k-space this may not be as much of an issue because it is far easier to get back to a structure if it is engaged. Between med clones, cynos, and interceptors, breaking through an attempt to block you from your structure is bound to fail. This is not the case in wormhole space where you could be engaged in a completely unrelated activity, podded back to k-space and rolled out of your system by the changing landscape.
Yes, any wormholer worth their salt will have an alt inside the system in order to either scan themselves back out or to man the defenses. But this brings us to the second point
2. Structures are vulnerable to attack by a single Entosis equipped ship
Instead of having a large EHP barrier to deter causing attacks, wormhole structures will now be vulnerable to a single ship. Note: It has been stated by CCP Nullaboar that vulnerability timers will not necessarily be everyday. This is definitely an improvement to the daily dedicated defense requirement but is still problematic.
Not only are they vulnerable to only a single ship, but these structures will not defend themselves against that ship. This means that any prudent wormhole corporation will be required to dedicate a character, per structure, to be in the structure during the vulnerability window. To do otherwise would be foolish. You can't PvP or PvE or do other wormhole activities during this window for fear of being podded from your system rendering all your structures and assets vulnerable to reinforcement.
But Obil, there will be a series of reinforcement periods. People won't camp out in wormholes just to reinforce a system day after day!
[pause for dramatic effect] [insert laughter here]
I guarantee you this will happen either by people logging off in foreign holes, seeding alts into holes for harassment purposes, or by the sheer fact that the barrier to attack is so low that every passerby into your system noticing a reinforcement period timer will attack because they can.
But Obil, this is true for k-space structures and they aren't going to put people in their structures all the time to defend them. You're right. They're aren't. Mostly because their entire corporation's assets are not locked into that structure. There is also a near zero chance they could be expelled from their space, pod and all, with no means of returning. They can quickly return to their structures for defense when the attack comes. These are unique problems to w-space. I believe that fixing the first issue will go a long way to alleviating my concerns here. A tower that can mount a reasonable defense without a pilot present will deter casual, drive-by reinforcement.
I will say that small k-space corporations are at a massive disadvantage under this system also. High-sec at least will have the 24 hour wardec period as they do today but low-sec and null-sec small corporations will be very vulnerable under this system without structure defenses to the point I would be surprised if many would retain their structures.
3. Structures can be anchorable anywhere in space
This is both an offensive and defensive problem for wormhole activities
Offensively, by allowing structures to be anchored away from celestials (moons), you destroy any ability for a covert scout to determine structure locations and to observe activities without launching combat probes, a module which takes a considerable amount of ship fitting to use. This could be resolved by every anchored structure being visible on the overview and warpable. I'm not sure this is a great alternative but it is, at least, functional.
Defensively, the potential for invading beach-heads to be set up is huge. While not every occupied hole is moon-locked, there is, at least, a finite number of attack vectors to any given system. Structures anchored anywhere in space is a massive potential problem especially considering the multiple vulnerability windows and timing. It could be massively difficult to remove an invading force that actively occupies their structures, sets vulnerability windows counter to the residents active zones, and anchors many many structures making the effort involved in removing them even more insurmountable than the EHP walls of today.
I struggle to see the advantage of free anchoring of structures given these issues.
4. Assets are placed into safety containers upon structure destruction
W-space is badly in need of conflict drivers.
This change single-handedly destroys the only motivation people have to attack structures (for profit). Combine this with the incredibly low barrier to attack, the standard procedure for anyone in w-space may be to attack every structure they see that has no one at the structure when they arrive. There is no loot to be had so why not attack all the things, all the time, every time just for fun.
Once again, structures auto-defending themselves will prevent this LOL behavior from becoming commonplace in w-space.
New structures must have automated defenses capable of preventing casual attacks during vulnerability windows
Structures (especially in w-space) should still be anchorable at moons only. Open anchoring presents too many issues without any discernible benefit or enhancement to gameplay