I'm happy to leave this issue up to the Debian maintainer, since the upx compression would need to be done in the packaging process and doesn't involve upstream.
I tested upx compression (with --best --ultra-brute) on macOS. Time for 'pandoc --version' went from 0.031s without compression to 0.756s with compression. This is potentially an issue for some users of pandoc (particularly people who shell out to pandoc to convert small bits of text). Offering a compressed version as an option sounds like a good idea.
