If you are a developer, please build MegaGlest on your own and get in touch to contribute (or post your patches on the forums).
In general laoding compressed files does not speed up laoding! Compression makes it better for transferring files, but loading will actually slow down since you ultimately must decompress. The best ulternative is to use better fgile formats. In Mega-Glest we added support for png and jpeg textures so that may load faster than tga. Thats just guesswork mind you as I never tested the speed differences.