Mark Bernstein brings up the idea of thinking of links backwards-- everything is linked to everything else, and you as an author determine what *prevents* a visit. (Mark wrote a paper and presentation about a card game Thespis to model this.) Then set several players (agents?) who get points for going to certain lexia and provide links... and you've got structure. This goes back to the idea of a link server which revises the link structure for you based on criteria. What rhetorical structures (besides programming) will make the sculpturally, thespis-like approach accessible to authors? A timeline can help you set this up for a static site, but it's still dauntingly complex to make. And people will find the game analogy anaethema, not serious.
Also, the UI is difficult. You need an interface like the path builder, or like Windows Server's "resulting policy" feature which shows you: at this point on this path, what are my constraints and conditions?" Also, "what can't I do?" (Plus: do you show the reader that so that they have a sense of how far they've gotten through the potential of a text?)
There are some big challenges with the Thespis approach. It requires knowledge of the text; it is authorial only. Since it's drawing from a pool of lexia, the text itself must be compelling or the reader starts playing it like a game because the conditions become the focus of reading. If you can see where you're going and where you're not, a game develops around getting places.
In the metaphorical setting of thespis, what about false cards? Cards that a reader should play, but which reconfigure the goals like a game of Fluxx. At this point the people at the table wanted a way to see that possibility, a way to communicate loss ("cards you'll never see are..." or "this link has precluded you from...". Doing that discourages a linear text or linear reading. One interface for this might be a sort of possibility graph-- as you play cards your hand grows, shrinks, and eventually dries up. Parts of a map grow dim as they become inaccessible (or read)
There's a distinction between games and hypertext in the outcome. Having the outcome always the same might be bad game design, but good hypertext. It's a matter of agency and identification with the protagonist. The character in a good text, as in a game, must be limited.