Assuming you get the categorization subscriptions to work, it should be sufficient to broadcast the category and associated products and have each endpoint just ignore the products it doesn't care about. Otherwise you'd have to create a message per product and include the category so endpoint can ignore configured categories.
The 'PubSub' example that comes with NServiceBus demonstrates this scenario.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.