Here is my ModMaker tool for C&C3 Tiberium Wars. It should be able to mod the demo, the full version, and World Builder.
It takes a few minutes (literally) to decompress some of the large files the first time you use it. But it decompresses them to temp files, so after that it should be fast.
There has been a report of it filling memory and doing nothing. That doesn't happen on my computer. If it happens to you, let me know. I have only been able to test it on the demo.
http://carl.kenner.googlepages.com/cnc3