Project Organization using Maven + Git
I have a maven project consisting of over 60 modules, and my team has discussed the same question of exactly where the git repository roots should be. So far, every discussion has ended with leaving the entire project, all the way up to the root pom, in the same project. The decision is mainly based around developer convenience--we don't have to clone and open multiple different repositories to work in what's essentially the same project. The question of history seems bogus to me. Who cares if the history is blended? You can always see a particular file's/module's/path's history in git, exclusive of any others.
An option we've considered is something called git submodules, which let you embed repos within repos. This could be an option for organizing your hierarchy if you decide to break it up.
I would suggest to leave the structure in Git the same as in SVN which means a single Git repos with the whole project in it. The point is you can use the Maven release plugin without any problems for such kind of multi-modules builds.