I have a repository which I have already cloned from Subversion. I\'ve been doing some work in this repository in its Git form and I would hate to lose that struct
You probably want to look into git-filter-branch, specifically the --commit-filter option. This command is a powerful chainsaw that can rewrite your entire repository history, changing whatever you might want to change.
Note that when you do this, you should pull new clones from the updated repository since the SHA1 hashes of every commit may have changed.