Instead of putting a dotfile or dotdir in the user's home directory, do follow the XDG Base Directory specification: http://standards.freedesktop.org/basedir-spec/basedir-spec-l... . It's easy to understand and requires only a marginal increase in effort/code.
I notice the $XDG_DATA_HOME environment variable isn't set in my Intrepid install. Maybe its set in later Ubuntu version. But the value not being set for me means implies to me that it not being set is pretty common. Thus it seems like supporting this standard is going to involve supporting a fall-back of whatever you would do otherwise. So I don't see "easy" at all but rather extra BS. Sorry.
Also, for my 2c, you should consider updating your Intrepid install if you at all can. It hasn't been supported for over two years, so it hasn't seen any security updates in that time. The Ubuntu do-release-upgrade system is pretty easy and reliable.