Put same folder structure into folder, that has highter read priority and you can change any sound, texture or voice. When Repair.exe does not detect anything, because NOTHING CHANGED in MPQ archives!
As example. Folder LibertyMulti.SC2Mod has highter priority, than Liberty.SC2Mod. Then put into this folder enGB.SC2Assets (MPQ file from folder Liberty.SC2Mod, that has lower read priority), recreate all folders structure, put new files, and play with new voices, sounds or textures without editing any MPQ!
MPQ Editing is bannable, but adding files into folder, that has highter read priority is not described anywhere in the license agreement