Limited store only makes sense to a certain degree and really just for the handhelds. Everything in the PSP and PS1 specific since that's the stuff that can be used on the PSP (aside for trailers etc. for other platforms).
Then the Vita needs access to everything the PSP has it's able to use all of that plus the vita specific stuff such as Vita games and Apps.
Then the PS3 needs access to everything the VIta has as the PS3 acts as content storage/manager for both PSP and PSV. That, plus PS3 specific items and PSN games. This is the reason why the PS3 store is so stuffed but it kinda has to be. Some people simply need the PS3 to get the most out of their handheld.
The PS4 may lose some PS3 specific content if PS3 B/C won't be present but it still acts like a hub for the portable, or at the least the PSV.
Also, the Vita pretty much confirms that PS4 will have cross-game chat. Actually, now that I think about it... the Vita covers almost everything you've listed.
4 ≈ One
