Ok, you already know I hate CPY...IMPF so I'll leave that alone.
But why create a new file with DSPOBJD when you have a file already out
there with all those tables in it?
It's been on your system since V3R1 so I'm thinking it's time you learn
On current versions of the OS you can read the file QSYS2/SYSTABLES.
On older versions (down to V3R1) you can use QSYS.QADBXREF
But if you've got the space to waste,
and the time to waste generating a new file,
then, by all means, continue to use DSPOBJD to an output file.
Newer versions of CPYTOIMPF did add the ADDCOLNAM parameter. Prompt that