id Software said in an interview that their Rage engine might be a bit too complex for modders because of the megatextures:
"Unfortunately, Rage is going to be more difficult to mod," said Willits, primarily because of the complexity of the game's vaunted megatexture system, which stores the texture data for levels as one huge texture map that streams in, rather than many smaller textures.
Megatextures require huge amounts of processing power to be baked into their final form for distribution on the game disc; Willits alluded to a large number of computers working for a long time to process them, analogous to a CG render farm.
Willits envisioned modders developing modular chunks of gameplay that can be slotted into the extant Rage world, rather than full mods, as a potential solution. While the game's large central wasteland is a streaming hub world, its levels are instance-based.