Since your ultimate goal is to trace the history of information in the system.log files, you could, as an alternative, try
grep from the command line, and search all system logs at once. I'm not a pro with
grep, but looking for something like "shutdown" in all logs could be done via:
grep shutdown /var/log/system.log*
This would produce a single output with any line containing the word "shutdown". The
* at the end is a regular expression that expands the search to all files starting with
system.log, regardless of the extension that follows (e.g.,
system.log.0.bz2, system.log.0.bz3). If you grok regular expressions, aka "regex" (I do not), then you can further augment this kind of search and make it ridiculously powerful and specific. You can check out this link and this link for more information about regular expressions.
Also, if you wanted to view the results outside of Terminal, you could pipe the results to a plain text file via:
grep shutdown system.log* | ~/Desktop/results.txt
I realize this doesn't restructure your system logs, but it does get you the end result you're looking for.