Er, wouldn't that run into a notable issue wherein your bubble can only travel at sub-light speeds? Unless I'm missing something, most excitement for something like a warp drive would be interstellar distances, which... well, seem like would still be an issue if you've got to cart around a bubble of space with you.
Space can expand (and contract) faster than the speed of light in a vacuum, as it did during the Big Bang, for example. The Alcubierre drive is basically a cheat, by contracting and expanding space in front and behind your ship, you can go from point A to B in as little time as if you moved faster than light without your ship actually doing so.
"Any technology distinguishable from magic is insufficiently advanced."
Gehm's corollary to Clarke's Third Law