Allow me to echo my support for:
- More powers triggering off of CA beyond a rogue/thief
- Rules for mass combat/armies
Also, I think there is room to bring back uber-bad-ass character defining magic items like you had in 2E (i.e. Holy Avenger, Staff of Power, Ring of Invisibility).
To give these rare items awesome powers and keep them balanced, you simply give them powers that are "Restricted". Then you could just add a feat or an Encounter power that every class can take that gives someone access to a rare item's Restricted power. e.g.:
Vorpal Sword - has all the standard properties/powers commensurate with the current crappy excuse for 'rare' items. Then add: [Restricted] (Encounter) Trigger: You hit with this weapon. Effect: Add 4[W] damage to the attack.
The owner would take the Encounter Power "Restricted Magic Item Power", which says: You can use the Restricted item power of a magic item of a level equal to or less than this power. (The Encounter power would be available at every Encounter power level, higher level ones just unlock higher level items, which of course will have better powers. A low-level Vorpal Sword might only add 1 or 2[W].)
Then you can have a Staff of Power that actually lets the owner use it to launch lightning bolts and fireballs at enemies, or a Ring of Invisibility that actually regularly turns its owner invisibile.
A feat could be used for more rinky-dink properties of items. Boots of Speed give +1 speed, but have a restricted property requiring a feat that gives you another +1 to speed.
You could drape a Holy Avenger in awesome powers (like the dream item it used to be), with a lucky owner spending multiple Encounter powers/feats to get its full benefits such as an Encounter power to deliver a devastating blow of radiant damage that stuns a target. Bonus to saves against all Fear, Charm, Psychic attacks. A daily power to resist 10 all damage for the battle. etc... items would be cool again!