So kawers have you ever wanted to put maybe a circle of element but you want the power of a cursed foundry? Why not be able to switch the stats of them so you can have the building you want plus the stats. Does that sound good?
For the spies let's say you want oso instead of ovary, you would pay what you would pay for the ovary for the oso but the same stats as ovary. Think that sounds good for the spies.
Don't you just hate it when you go to build a volary and get an ovary instead? Especially when you try to play at certain times of the month...