I'm confused whether you're talking about audio or MIDI clips. With Audio clips that contain clip automation (gain or pan), you can't copy solely the clip automation. MIDI clips don't have "internal" clip automation, they are affected solely by track automation, which as you point out can be copied and pasted via the piano roll or of course, using standard track automation. If you select a MIDI clip, "copy special" it, and choose only automation and not events, you can impose that envelope on another clip.
So is what you want the ability to have MIDI automation within a clip, the same way audio clips have gain and pan, and be able to copy those clip envelopes to other clips independent of track automation?