Hi Dimitris,
I don't think downloading a file and opening it (4 o 5 mouse clicks?) make the translation process hard for nobody.
As a translator, you may have 4 or 5 PO file to translate (doing a great work!) but as a coordinator, you may have those 4 or 5 PO files to review and commit multiplied for your active translators, plus your own PO files... sorry if I make my translators life harder, but I also have limited time, and need a tool that helps me to quickly review a translation and also lets me track the module's translation history.
Also, we have several roles: translator, proofreader and commiter. Hiding GNOME's infraestructure to plain translators may avoid them grow up and acquire knowledge about how translations workflow works. If I have a lot of translators but have no proofreaders nor commiters, workflow will be slower, and the number and the quality of the translations will fall down.
In the other hand, it has also benn commented above, Transifex doesn't work directly with the repo, so statistics are not reliable.