Hidden Tech Triggers
So I was reading Frogboy's tech thread and was excited about the prospect of "hidden techs," so I've detailed an idea for the emmergence of hiddens techs.
I think the likelihood of a player getting a hidden tech should be contingent on the the player taking part in the activity of which the tech would be found. In other words, you are more likely to get more hidden techs related to woodworking if you are an empire that employs a lot of wood working, more likely to get more hidden techs related to alchemy if you use a lot of alchemy, etc. Besides, it would be silly to gain the "Alchemist's Fire" hidden tech if you don't have an Alchemy infrastructer. First, because it makes logical sense that a civilization that uses something a lot will innovate more with it too and; second, you wouldn't have the infrastructure to put it to good use otherwise.
I think that hidden techs should have certain triggers that raise the probability of them being visible and researchable by the player. These triggers could be almost anything. Hidden triggers could be anything from certain buildings that you own, to soldier types that you employ, to dungeons that you've romped, or the number of times you've cast spells from a certain school. Modders could create thousands of hidden techs which could have any kind of effect on the game with virtually any trigger.
For instance, there might be a hidden tech called "Iron Wood Spears" which has a 1 percent chance of appearing at a specified point on the research tree for every lumber mill that you control. In the above case, there might be a total X number of hidden techs in the game, some of which might be discovered by two or three or four different sovereigns and some never at all during the span of the game (if not many people build Scholar's Guilds--- which is the trigger for "Dancing Quills"--- it's unlikely anyone will discover the hidden techs that uses a Scholar's Guild as a trigger.)
And while you may have gotten 1 hidden tech opened to you at that specific junction of the tech tree, you might have missed 10 others.
Another twist might be that only 1 sovereign might be able to get a specific special tech. It would work by counting up the total number of triggers currently in the game from all opponents, (let's say in this case lumber mills) calculate the percentage that each sovereign has and then distribute the tech to one of those sovereigns, with higher percentages attracting higher odds of being the recipient.