Howabout a culturally-linked researchable checkbox, so some techs can only be gained through trade with other civs that can research it? For example, Europeans can only discover gunpowder if they come into contact with Asians (or maybe build Marco Polo's Embassy...) Romans can only arm their legions with the gladius if they contact Iberian Celts. You wouldn't need EVENTS to do this, then.2. A tradable checkbox (default on). We can define whether each specific tech is tradeable or not or whether or not it will be discovered in goody huts. This means you are forced to research some techs. Also, techs in the "none" era can be defined as tradeable. So maybe each civilization can be given unique techs but they are bargainable.
Basically, non-tech prerequisites for techs, culturally-linked as with UUs in the Editor.