Any article about the differences (updates) between the Empire Army books? 
I don't know but there's always a lot of chatter in the forums when editions change.
As you noted, 6th edition dumped a ton of stuff from the Empire list. This created a simpler, more effective, human only army. More effective but a lot less interesting, I agree.
6th ed dropped the Halflings, Dwarves, Ogres, Kislevites, Reiksguard foot, outriders, monsters (and swarms), war altar, war wagon and the steam tank (though it was added on later through White Dwarf when they made a new metal version). Not to mention the removal of allies rules. That's a lot of stuff when you think about it
6th ed added the free company which was simply an excuse to sell more Mordheim mercenary sprues. A very good excuse but an excuse none the less. Huntsmen where a new feature as well as the division between militia and state troops. The engineer was introduced and handgun units could now have a champion armed with a Hochland long rifle or a repeater gun. I'd talk more about characters but characters don't interest me much.
The detachment rules were also improved for 6th ed. They could now counter charge rather than sit around twiddling their thumbs until it was their turn to move like in 4th and 5th ed. Handguns could now fire every turn (still move or shoot though) instead of every other turn and added an exta d6 inches to their range on their first turn. Pistoliers had their fusilade rule.
I haven't played any 7th edition yet. I think I'll be skipping this edition entirely. I do know that they reintroduced the outriders, war alter and added the rocket launcher. The rules were mucked around with a bit too.
As far as I know, there has never been an official dragon mini for the Empire army. You just have to use dragons from other armies.
