The heroic tier adventures would be focused on exploring the island and establishing various bases. Each region of the island would essentially be a single, large adventure with a primary theme and few possible threads throughout. There would be totally random encounters to be had by wandering through the zone along with encounters that are pointed to by the central theme of the area. As the players complete encounters in certain ways they get the option to set up certain "bases" for the different factions. Using the elf wood as an example again:
- Completing the Thunder Cliff encounter and firing the cannons will affect the elves. They are ready to be forgiven by the gods and a Chapterhouse can be established. Also, they'll be friendly enough to establish a trading post for the Trade Guild.
- The elves are dealing with a corruption in part of their woods - twisted, dying trees and such. It is coming from a gate to the Shadowfell. The Stone Circle wants it closed and will establish a Grove there if it is. The Tenebrous Cabal wants it kept open but needs some beasties cleaned out so they can establish a Sanctum.
- If key elf outposts are eliminated, the Legion can move in and establish a Fort.
- The elves' Tree of Life creates a zone of fey magic and is guarded by them jealously. The Imperial College would like to set up a Research Tower there to study it closer.
- In addition are various lairs for forest dwelling beasts and some scouts from the Feywild.
Once the final region has been claimed (most likely the central mountain that has the Seekrit Imperial Records) the PCs get some time to rest and enjoy the fruits of the labor. Then everything goes pear-shaped as the Feywild sort of drops down on the Island around them. The second part of the campaign is going back through the Feywild version of the island and using the settlements they've established to free it from King Oberon. If they don't, he'll use the island as a launching point to claim the Empire of Ammath like he did the old one
Once the island is secured the PCs take the fight to Oberon in the Feywild version of the old empire.
(As you can tell, the first part is the most interesting part - the Paragon and Epic tiers could easily be changed or it could just end with Heroic.)
Unlike most of the ideas I'll post here, this one has next to no house rules. It would be straight-up 4th edition D&D. Instead there would be the extra system for handling overland exploration and the meta rules for establishing and benefiting from settlements. For whatever reason, 4th edition tends to make me want to shape the world to it rather than shape 4th edition to the world. It may be because it is the edition I'm least familiar with or perhaps because compared to other editions it is more of a complete game.
This game seems like it would be fun to run. It could consist of just good old fashioned exploration and adventuring but the existence of the factions and their goals would allow for more emergent gameplay to evolve. The exploration and "capstone" system (that's what I call establishing settlements in each area) give the metagame a sort of boardgame feel that seems to match 4th edition well. It also has a few definite ending points and goals so that the campaign doesn't just meander until it runs out of steam. (Though the first ending point is too far away for my regular group who like to switch games a few times a year. Hence a Game I'll Never Play.)