Is there a way of applying skew/perspective to a track after applying track motion to reduce picture size. Or some other way of applying perspective to, say, credits, both rolling and 'normal'.
check out 3d track motion. Will add to render times, but will do what you want. "warning" though. It will apply to EVERYTHING on the track, so it's best if you want only a few clips to use track motion, make a whole new track for those clips.
You could use 3D track motion, but it might be overkill. The Deform video FX will also do what you need. Start by dropping one of the Squeeze presets and adjust as needed.