I want it so i can access the in game xmb, point at a friends profile and select an invite option. This will then send an alert to said friend who can then accept the invite, this will quit out of their current game and once the relevant disk is inserted the game will start and auto-join the server they were invited to.
While i can see this may require patching for older games i fail to see why it's impossible, it's going to require less effort to implement than the in-game XMB took. Even if it was a feature only available for patched or new games i would be happy, it's the fact that the XMB currently offers no form of invites for developers to work with, even though the in game music app isn't ever used i'm not annoyed as at least Sony have offered it as a feature to devs.
Your right in that it should be easy for Sony to implement something like that, but because of the way existing games all do their network stuff in their own way (I don't think there's any 2 games which do it exactly the same!

There is a basic invite system already (Send an invite from ingame - provided the game supports it, the other person receives it as a message then has to manually load up the game then accept the invite once their ingame), so there's no reason they couldn't expand on that in future.
One other thing I noticed this morning when I was checking it out was a divx VOB registration code (or something like that) in the video settings section - anyone know what that is for?