Meteor swarm has been implemented in lots of games, it doesn't level cities if its the same range as ice storm, just bludgeon & fire with higher damage dice instead of bludgeon and ice.
Level 9 and epic spells have been done in lots of games, they arent difficult to balance.
Maybe they shouldn't be balanced. Maybe the most powerful spells shouldn't be reduced to satisfy the needs of some generic video game progression that never ends. You're level 20, then what? You start nagging devs for level 30 and 10th level spells that do 2d6 more damage.
Higher levels start with higher level content. If the content doesn't exist, neither should the levels. It's as simple as that.
