I'd like to chime in my thoughts, even though I recognize this is a old, dead post. I stumbled upon this simply googling the idea of "warping into a ship" and it fascinates me.
First, I'd like to say that it is a damn shame this hasn't made it into a series episode or movie, especially considering the way the TNG movies were so action-driven. A collision-course-at-warp would really have wowed audiences.
The "technical challenges" of this maneuver seem trivial to me given the facts: starships have ultra advanced computers and seemingly perfect warp timing capabilities (if you can recall the VOY episode where they burst-warp through a maze of obstacles). Shuttles or even ships can be piloted by a single person or remotely if need be, minimizing loss of life. Borg cubes are not the most agile of ships, I doubt one has the ability to move out of the way fast enough to dodge a vessel at warp, while simultaneously engaged in combat with other ships, and finally, one would only need to engage warp from a distance just outside the cube's weapons range... or maybe even within it. The cube could anticipate the move by scanning the ship you say, well then do it with a cloaked ship. Why not warp into a cube from right next to the cube? Maybe you'd choose to be further away just to "build up more speed". Overall it seems like a cube is a target that's hard to miss, and that doing this might be well justified if the cube has already taken out 38 of your ships with no signs of stopping.
I present an alternate "explanation" as to why we've never seen this rockin' awesome maneuver:
Could it be that the materials starships are constructed from have a strength-to-weight ratio that is so high that the inertia of a starship collision would actually do little damage, even at warp speed, as compared with the starship's weapons and warp core detonation?
or... OR... that the fake laws of physics dictate that a ship at warp actually has very little inertia... somehow.
