I am always amazed at the amount of work people will go through in an attempt to avoid addressing the real problem. The irony is that the project inevitably looks half-assed and ends up costing more work and materials. You're going to hang a liner and wallpaper to hide rough walls? Wallpapers are not inexpensive and require alot of labor to hang. Fix the walls!

Indeed, the moisture and schrinking of the wallpaper as it dries might even aggravate the bad adhesion problem that already exists on the wall.