So I was thinking (always a bad plan) that Icecrown Citadel feels a little small to realistically represent the citadel of the Lich King himself. So using some photoshop (Gimp) magic I present a rashly thought out larger Icecrown Citadel.
In this expansion we see the citadel holding 25 bosses and subdivided into five sub-instances gated such that the completion route is the outer ramparts, the four inner sections of the Necropolis, then the upper fortress leading to the frozen throne.
Lets take a look at the overall concepts:
The Outer Ramparts
This consists of the current four bosses. Our heroes enter from a back route from the Pit of Saron encountering Lord Marrowgar and his minions, eventually breaking into the lower sanctum of the Death Knights and Lady Deathwhisper.
These two sections should feel a lot like a break into sections of the citadel we don't normally see, the resurrection chamber and the Death Knight barracks leading into Lady Deathwhisper acting as a priest to the newly risen Knights. This lets us break through from the rear into the ramparts where we destroy the anti-air defences (think 3 mini-bosses guarding anti-air guns), and mount our capital ship rising up towards the main citadel body.
The Inner Necropolis
This section (vaguely reminiscent of Naxxramas... well they had to get the architecture somewhere!) houses four independent wings unlocked by the death of Deathbring Saurfang (Killing 4 bosses opens your raid-lockout to these 4 instances, clearing all 4 of these opens the upper citadel). Each wing is themed as with Naxxramas hosting Plague, Construct, Death Knight, and Risen. Each wing can approach any boss in any order however like a giant version of the Assembly of Iron doing them in different orders results in different power levels and the true hardmode of each boss being doing them last (or activating the alarm on the section to activate all hardmodes).
As each section is independent it allows guilds suffering on a single boss to attempt progress on the four different wings, while allowing pugs to complete the first four then join upto four different pugs that week (or a single really successful pug).
This large section gives us a really strong way to gate the instance as a whole, 18 bosses spread over effectively 5 instances means we can produce a very difficult first area with this area serving to make unlocking the upper fortress difficult.
The Upper Fortress
The upper fortress is exactly what we have already, the commanders and research arms of the Lich King's forces. This section should ideally be ungated however with the bosses being harder.
I would like to really see the hardmodes of these bosses being tied together, Rotface and Festergut must be engaged on hardmode to trigger that of Putricide etc. Each of these fights should have a much stricter DPS, Healing and Tanking requirement than the lower citadel. This area is designed to force the players to really focus and test the players even on normal modes with the hardmodes being equivalent in difficulty to the Lich King at least.
The Frozen Throne
Not much more to do there, the Lich King alone on his throne. I would have preferred to see this fight being much more epic with waves of adds eventually thinning to be the raid against the Lich King while our NPCs engage and distract the adds and lieutenants to give us our single shot at ending the menace.
Gating the Instance
Simply gating based on a strict timetable is a little dull and limits the playability of the game. I would like to see this instance treated more as an event rather than a raid. The two weeks prior to the unlock of the outer ramparts begins with a series of 5 man and daily quests relating to Pit of Saron and the breakthrough into the under citadel.
Once the instance opens we have two active bosses, Lord Marrowgar and Lady Deathwhisper representing the reclaimation and newly risen Death Knight areas of the citadel. This section is not linked into the main body of the citadel so we instead break onto the ramparts starting the second set of events limiting the ammunition and downing the mini-bosses on the ramparts to enable our capital ships to fly into the airspace. This runs concurrently with Deathbringer Saurfang's mini-event to gather explosives and munitions to break through the citadel's armour.
Once we are inside the citadel itself we have four wings of the citadel. This section is cut off from the upper citadel due to a lack of power caused by our penetration efforts. Each end zone boss downed combined with a series of daily quests allows us to gather power cores to charge up the internal supplies of the citadel gaining access to the upper citadel.
The upper citadel is gated by progress, overall boss kills within the citadel and daily quests on each of the three zones (plague, blood and frost) result in forcing the lieutenants back into the fortress to defend their zones. The death of all bosses unlocks the Lich King himself.
I think I should leave this to a different post, trying to cover 25 bosses in a single post will likely be hard. Overall the idea is to make each boss more involved and the hardmodes especially punishing rather than the walkovers that many were.