Then you would be one of the first not to complain about this. But yes, in your comment lies the basic problem. How would guild assets or the guilds themselves look on the instances where the guild is not present? For the groups and the solo players, it would be a station/mining base/whatever bereft of life, since the only ones working on it are players. If such an option would ever present itself, I would say it would be only fair to take into account how such an asset works in the universe. As in being maintained and paid for by a minor faction with tens of thousands of possible subjects. So it should incur a high acquisition and high maintenance cost, which would represent keeping the asset running, and paying for all the npcs who actually work aboard your asset. Then it wouldn't be something lifeless in the other modes, and would make more sense to have multiple versions of it existing, as the npcs themselves would inhabit it in the modes of the game where the player owners are not present. But that's just an idea really.
And honestly, from my point of view, assets like that are the last thing I want to see implemented.
Instancing by location would seem to be the only plausible way to do this.
I'm not sure if CZ instancing is already done this way in Open mode.
But yes, players in Solo mode could present an issue.