I'd also prefer a generic artifact to upgrade any evolving building. A specific artifact reward is meaningless to players who have fully evolved featured buildings... nothing substantial to play for during those weeks.
I believe there is need to rebalance spell fragments from the Library, I have almost 300k in my live world city (chap 15) and already have more than I can use in beta (chap 6). I am crafting in both cities almost 24/7. However, please don't take the building set away... the population, goods, and culture are valuable.
Portal profits may be unusable below chapter 6, but should be allowed as an incentive to make it to chapter 6 and beyond. Else, I see this as yet another way to slow player progression.
I don't see the need for 100% supply or coin instants; there will be some wasted amount if a player is not at zero... and after the first day, I've never been at zero.
For me, I'd be most inspired to play in the Spire for:
* Diamonds
* Catalysts
* Time instants
* Teleport spells
* Manufacturing enchantments
* Magic Residences/workshops
* Other buildings with a chapter related amount of population with or without goods productions.
* A generic evolving artifact I could use on the evolving building of my choice.
Else, how about a player's choice reward? We all don't need or value the same prize. So maybe a choice between 3 chests each with a different main prize?
respectfully submitted