Using RePair for compression I can also search inside compressed tarballs full of logs

To do this, I first insert a blank line at the top of each log file before adding to the tarball

IME, RePair is faster than compressing with zstd and the size reduction is almost the same

The only "catch" is that RePair requires more memory during compression

Pardon, but do you have a link for this RePair compressor?

Unfortunately, different searches for this RePair you mentioned have only revealed links to resources for repairing broken air compressors, damaged compressed files, spinal injuries, etc.