I meant the standard diff: en.wikipedia.org/wiki/File:Meld_file1.png
It is important to have it in tools.percona to be able to play with different configurations to understand how much memory, resources will be requested by database. And also having dozens of MySQL installations it would wise to keep configs in one place and compare between them.
Then in the query analyzer is would be nice to keep track of diffs, so you may tune your monster query and keep all diffs in one place.
I see what you mean now.
Note that memory usage in the end not only depends on configuration but also on several other factors, so it's not that straightforward.
For dozens of MySQL installations I strongly recommend to use central configuration management like Puppet or Chef with MySQL configs as templates. This way the same parametrized template can serve for many different instances. This together with SVN or Git will let you keep perfect track of each configuration file and it's changes.
tools.percona.com is rather focused on very MySQL specific subjects so I don't know if such functionality will be added.
Currently we're using gist.github.com to organize and share different configurations, but it lucks the profiling. So we have tools.percona for profiling and gist for sharing and online collaboration. Shouldn't it to be the one complete app?