Maybe allow switching of spells ready for battle in army camp with spells brewed but waiting for place to be able to be used in battle. E.g: player trains enough troops for 2 attacks and brews spells for both as well. Then he attacks the first attack but doesn't use all spells. Now he is stuck with spells he doesn't want for the second attack so if he could switch them out with already brewed spells he will be saving elixir and time. Better farming, happier farmers

