Its not a TES thing, but then again its not a RPG thing or any genre or game so far for that matter. The idea is simple, wouldn't it be cool if in addition to the variety of well known skills there were a number of hidden skills talents and professions you could discover in game with much difficulty, Sort of unofficial quests, and not in an overly hyped way or anything, but I want it to be precisely that, a mysterious almost unmentioned thing that doesn't jump out at you, but you just discover in your research and journeys through the game. If this is just me please tell me but if the concept appeals to you I'd like to know. I'm leaving this intentionally vague as I want to hear ideas, I have a lot of my own, but I really don't want to limit discussion by implying any sort of specifics in the first post (But just as an idea, think of leveling of as a vampire, or learning necromancy? Hint hint).

Published guidebooks + Internet make it futile. The info would also be in the construction set for all to see.

I'd actually thought of that . The older TES programmers have a lot of experience with procedural generation from the development of games before Morrowind. It wouldn't be farfetched for them to make the discovery and pursuit of these skills a procedural process that was different for every player, making it impossible to develop a guide for all players, and also making it a much more unique experience and rewarding experience for all players.