The other thing to remember is that Halo lets you create your own custom objects to place in CShop. So if you want a spaceship and tilt it in the World, as Sswift suggests, you would create the spaceship on it's own, then load it into your map as an object and you can move it around with it's own UV coordinates remaining constant.
As Joe says, this is the way CSG level editors usually work. If you bear in mind that ever wall is a separate object, and often consists of several objects per wall, using world UV coordinates for objects is the only way you could build the basic levels without going nuts. Imagine if every time you moved a step it stopped tiling with the rest of the floor. You'd go nuts. I think the answer might be to get used to creating items on their own and then placing them into maps.
As Joe says, this is the way CSG level editors usually work. If you bear in mind that ever wall is a separate object, and often consists of several objects per wall, using world UV coordinates for objects is the only way you could build the basic levels without going nuts. Imagine if every time you moved a step it stopped tiling with the rest of the floor. You'd go nuts. I think the answer might be to get used to creating items on their own and then placing them into maps.