Wind of Change

The idea of having a separate level/slot for control is excellent. Setting a fixed price (increased, for example, 20 resources for Town Portal, 30 for Dimension Door) would be a good approach. It shouldn't be removed from books/Pandora's Boxes, as it provides an alternative way to obtain it. This randomness in control within the game has repeatedly shown that something needs to be changed. The variance can be too extreme because in GM4, you can rebuild 4-5 times (13 spells), and in GM5, 5-7 times (6-8 spells). This results in a possible difference of 10-12 days! This idea has been discussed several times during streams with players, and a significant number of them support this approach.