The latest image from CCP's Tumbler account really gives some perspective to the scale of a Citadel, finally. With an Avatar and a Chimera parked off to one side the sheer enormity of the structure is suddenly brought into stark reality, and it's just a Medium! Unfortunately, it's probably brought a stark reality to a few hopeful capsuleers, myself included.
I admit, what I know about Capital ship construction you could write on the back of a postage stamp with a crayon, but judging by the scale of this structure, an extraordinary amount of minerals are going to be required and a highly skilled industry character to build it. The prospect of having a home base in W-Space that didn't require fueling is a lucrative one and I did have every intention of setting up one for both my bearing entities and with Sudden Buggery for our respective home bases. Now... I'm less certain about it.
For one, it's clearly going to take several weeks just to build it. That's a long time for someone in W-Space to find your Citadel under construction and coat hanger it. Secondly, if scaling is anything to go by, the mineral requirement will be enormous and almost certainly beyond the achievable realms of a small group.
Then you have to consider the cost. If a Titan is worth about, what, 60 billion these days[?] and the citadel is, at least by visuals, four or five times the size of a Titan, I think it's fair to say the ISK you save on fuel may take a while to pay it off.
With any luck I'm being an alarmist and going off half cocked over a few artist impressions. I know CCP want to phase out POS's in favour of these behemoths, and I'm all in favour of that so long as it's achievable for those of us not in the big NullSec power Blocs.