Let's see if I've got it right... Basically, you want an RSS feed to show on your front page...right?
If so, I think this should work:
1. Create a link to an RSS feed that you wish to put on your front page (from mainmenu)
2. Make this link the first item in the mainmenu. You can call it whatever you like, but 'Home' will do
You'll see that when you access your site, the first page shown is always the first link of your first menu (mainmenu), so if that's an RSS feed, then it should be the first thing shown.
This means no modules, no fiddling with templates, etc.
San Giovanni Rotondo