While it's kind of off-topic: Conversely, "floating" powers would also be quite nice, and could eliminate some measure of power bloat where the only differences are stat mods. Skill Powers are excellent examples of these.
Yes, actually that's a road I wish WotC would walk someday. They already hinted about classes being able to share powers ("defender's aura" for Knight and Cavalier, "leaf wall" in Sentinel and Hunter, skill powers, and so on).
I think it's not that difficult to achieve. Sure, it's quite hard to do into 4e (just like removing feats would be). But if you build the entire game with that in mind, it's not. Lot of powers do the same thing, or quite similar, in different classes. "footwork lure" and "luring strike" are quite the same thing, with just minor difference to make 2 different powers to what would be exactly the same thing otherwise.
I think the game could easily build "power lists". For example you could build a power list named "shield fighting", and put there a couple "shield block", "shield bash", "shield ram", "shield wall" etc. Then you can give access to it to any class you feel they should (ie: fighter -or some theme of fighter-, paladin -or some theme of paladin-). Thus a paladin, a ranger, and a fighter might have all of them access to the same "cleave", "sweeping strike" and "whirlwind", while only the paladin has access to "smite infidel", "exorcism" and "rightneus might", only the ranger has access to "twin strike", "double swing" and "hurricane of blades", and only the fighter has access to whatever signature power list you want to give them. You can even make it so no spell list is class only (ie: the avenger might get access to "smite infidel" list, and a dual wield rogue might have access to "twin strike" tree).
You could then give the classes some perks that modify the powers sometime, if you want to give each class a "special feeling" about the power.
For example, while the warlock, sorceror and wizard might have all of them access to "fire spells", including "burning hands", "fireball" and "firestorm", you could give the warlocks a trait named "hell flames" so all their fire spells grant vulnerability 5 to fire, sorceror might have "ignite", so all their fire spells do ongoing fire damage, and Wizards have "explosive", so all their fire spells knock their targets prone.
This will save a lot of space. Instead of listing 10 fire spells for fire themed wizards, then listing 10 fire spells for fire themed warlocks, then 10 different spells for fire themed sorcerors, you could just build 10 (or, as you have more space free now, maybe 20) different spells. Each class could have a unique and distinctive "feel", (That is consistent through all the list, as all wizard fire spells knock prone in adition to whatever other effect they do), and are easier to remember (once you have played a sorceror, you know how a fireball from a warlock works. It's the same with everything -range, area, damage, riders- except that you no longer use the "ongoing damage" but the "vulnerability" rider.