I believe most of that is correct, however lift characteristics are also closely tied to the physical geometry of the airfoil itself. If you're dealing with a symmetrical cross-section airfoil, ideally you should not be generating any lift in direct forward flight. With a cambered airfoil, the foil itself has a sort of AoA already inherent in the foil itself, meaning that in forward flight, zero AoA, the foil will generate lift when accelerated/propelled through the air.
With extreme speeds and extreme altitudes, this is what I see happening with a symmetrical, neutral lift at zero AoA foil (on a spaceplane, of course):
Given such velocity (also aided by the fact that low atmospheric density provides little resistance for the craft in question, aiding in high speed flight) and such altitude, the craft, despite being at 0 AoA in relation to the planet, will climb as its rotational velocity/acceleration (in relation to Earth) is such that it pulls away from the downward force of gravity whose origin (in this case) of course is the planet.
I can't say truthfully that this is indeed the case, but I'm pretty sure it's a valid argument. Thus, to continue accelerating in a line (which is actually an arc - it is a planet, after all...), you'd need to have a negative AoA. This would be even more apparent in an aircraft with a cambered airfoil...
