What it says on the tin, what if Brilliant Pebbels in particular, maybe even SDI in general, survives long enough to be deployed operationally in the late 90's or early 2000's
Interesting points regarding Brilliant Pebbles:
1: It was space-based.
2: It required more launches for less money than any (existing) launch system could have provided (or so I've heard).
Together, these give a strong incentive for a more reasonable X-33 program; say, adapting the DC-X design (it was, after all, originally developed as part of the development of Brilliant Pebbles), or looking at the Rockwell X-33 design. Mostly avoiding Lockheed Martin, their design was impractical and overly risky technologically.
What if you get a rogue state to launch an ICBM at somebody? With the precedent set for it, the US would have justification for pulling out of the ABM treaty. Of course this has all sorts of butterflies involved so a space based missile defense system would be the least of the changes.
What it says on the tin, what if Brilliant Pebbels in particular, maybe even SDI in general, survives long enough to be deployed operationally in the late 90's or early 2000's