RTF is a global modification that replaces all towns in the game.

1) Changing the territories (the native lands of dwarves are lava, the native lands of elementals are a desert)
4) The arena for the siege of the city of elementals will be the old one (on grass).

Where is the logic in that?
The territory is a desert, but the arena is grass?!
In general, if a Wizard or Necromancer exports some objects from Heroes 6/7 that are more or less suitable for elementals, we can make them a flying arena.

By the way, why did you decide to change the native lands of the dwarves?