Board Thread:Warhammer 40k General Discussion/@comment-72.240.130.242-20130618172401/@comment-3580035-20130619104653

The main point is that all Titans are relics. Its like saying you should take apart a Dreadnought's limbs and lay them out nicely in a crate for easy storage. A Titan's Machine Spirit is very temperamental, and will most likely die, if not go outright beserk and mad, if it gets taken apart and put back together.

You also can't just stick Warp engines in everything...For one, a Warp engine can be about the same size as a Titan itself, and you can only send large objects through the Warp safely (e.g. Ships; Titans are too small). Titans are also not the most aerodynamic of things and definitely will not get risked getting shot down if they are somehow flying in the first place.