Id software would like to hold firm to their position of allowing their games to be modded by the user community but Tim Willits, Lead Designer for Id Software, admitted at the Austin Game Developers Conference that modding Rage may be very difficult.
“Unfortunately, Rage is going to be more difficult to mod” Willits said when replying to a question from the audience as reported on Gamasutra. He went on to explain that this is due to the complexity of the games brand new megatexture system, which stores the texture data for levels as one huge texture map that streams in, rather than many smaller textures.
It may be possible for modders to develop gameplay modules that can be slotted into the existing Rage world but a complete remod of the game is probably not possible as it was with previous ID titles.