The issue is when a character has multiple classes that meet the prerequisites for Improved Spell Capacity, like a wizard 10/cleric 10/mystic theurge 10 has access to 9th level spells from both Wizard and Cleric. So, please vote:
- When the character takes Improved Spell Capacity, he gains a spell slot of a level equal to his highest level+1 in each class that qualifies for the feat. In the example above, the character would gain a 10th level spell slot for both Wizard and Cleric.
- When the character takes Improved Spell Capacity, he must select the class to which the benefit of Improved Spell Capacity is gained.
- I don't really know. Whatever the common opinion seems to be is fine with me.
- See post