I just tested this out while running HIP only. In basegame, if for example the King of Poland institutes Feudal Elective, and the Duke of Bohemia usurps the duchy of Silesia, the Duke of Bohemia/Silesia will be able to vote in Poland's election as long as Silesia is his primary title. I tested this running HIP and it did not work. You are an elegible heir, so you can be voted in, but you do not get the right to vote in the election yourself. What gives? Also, if this is to be fixed, then perhaps it should be extended to all de jure vassals? If the duke of Bohemia gets integrated into the HRE, he should still be able to vote for the King of Poland. That should be the same if the Kingdom of Poland gets vassalised too.
