Tadaamm! But, there's an indirect flaw (somehow) to this solution. The AIs must refer to a certain value for any of these ImpossibleTechs - which would, as a result, be created as a generally impressive (or not) target for either trading or stealing 'patterns'.
May seem a bit odd to the human player or even to both of us (if you consider the *willingnesstotrade* clause if and when applied!), but to an AI trying to parse what MUST be given a priority, i believe there has to be a conditional loop check in the algorithm to handle Impossibles in a particular manner; possibly, lowest priority in fact.
Thus, the boomerang effect to many trading circumstances.
Quite hard to explain without an attempt at some bad analogy;
- Race B really wants Superior Espionage from the Krynn.
- Krynn denies many times over.
- Drengin invades a Krynn planet, gets lucky and grabs it away from the Krynn.
- Race B contacts Drengin later on.
- Gets it from them.
All impervious to any algorithm checks performed on the exclusive TRADING status of a tech even if made Impossible at setup time.
Well, i don't have the source code. So i can only extrapolate based on many different hypothesis - one of which, unaltered conditions provided by default race trees.
Modify this simple situation, and you're certainly in for weird or unpredictable results including some complex AI 'reasonings'.