shuffle = no calendar for me, I don't waste the time, too frustrating. But, the skull cave is a nice building and will take diamonds to get. Worst case, 32x400=12800. So people with diamonds do have a place to spend them without spending direct $$. Not sure the price is worth it but that is a choice by the player.
Premium line, Viceroy at 340, not sure how that works out with normal play. At 280 you get L9 Traders Post. If you want people to spend the $15, move it to 280. YES, along with the Buccaneer upgrade given at the beginning. If you make it so we have to spend diamonds too, now you are double dipping on players. Obviously you are using the paywall to give options for improving our cities for GE 5, defending stats. One can wait for events and get improvements over time. Others can pay and get improvements for defending army faster and not have to change the building in the city. I can handle that business model. BUT, where you put it is important.
Double dipping us = NO BUENO
I will wait to see calculations but I don't think you are making a L9 Traders post @280 and the 30 fragments for the Bucc @300 a given. Plus, due to the nature of receiving hidden rewards, it can not be calculated exactly.
Treasure map - I guess you know how many people spend on it, I never have bought the full Elves workshop. I think it is a waste but others may like it.