This seems like a natural fit for D&D.Sci games. All the ones I made are public domain, so you can use them freely (and I bet the other people who made some would give you permission if you asked them nicely), they've been publicly played by clever humans with a variety of skill levels and associated outcomes, and they're obscure enough that I doubt an LLM would have memorized the solutions (and if not you could tweak the names and data-generation hyperparameters to flatfoot them).
. . . I happen to have a completed-but-unreleased D&D.Sci game, whic...
For the unreleased challenge, b) isn't for sale: making something intended to (eventually) be played by humans on LW and then using it solely as LLM-fodder would just be too sad. And I'm guessing you wouldn't want a) without b); if so, so much for that.
. . . if the "it must never be released to the public internet" constraint really is that stringent, I might be better advised to make D&D.Sci-style puzzles specifically for your purposes. The following questions then become relevant:
.How closely am I allowed to copy existing work? (This gets easier the ... (read more)