Anything I should change/add/modify in terms of encounters or to add a unique Eberron flavor?
I DM Eberron for a long time, and I just DMed Revenge of the Giants, but, I've decided to play the adventure in the D&d basic scenario 'cause I did found very hard to put the "Legendary City of Argent" in Eberron Setting.
Many challanges in the campaing must be revised in order to make a unique Eberron flavor. I say that 'cause ROTG have a lot of total deadly encounters that sound much like the old Ad&d adventurers like Castle Ravenloft or Tomb of Horrors, wich is the total inverse of the heroic flamboyant encounters from Eberron.
Anyway, I thougt a lot in how to adapt the ROTG to Eberron, and I have some ideas:
1 - Eberron did not had the Dawn War, so you have to find another source for the Primordials to hate the free races. In Eberron I think it's the fall of the giant civilization of X'endrik. So, your Giants would be the heirs of Giant Empire of yore, trying to ressurrect their land.
2 - Piranoth is a locked primordial, a recursive flavor of the basic 4th edition scenario. In Eberron, I do not like this idea. You could use the history of the setting. It's said that the Dragons and Coutl destroyed the giants of X'endrik 'cause they was very close to find some source of arcane magic that would be very nocive. Maybe this is Piranoth, wich, IMO, would be more a legendary source of chaos energy than a being.
3 - The City of Argent it's the land of a kind of Sacred Order created by a Godish Compact. Ok, no Gods compact in Eberron. IMO this is the hardest part to adapt. Maybe Argent is a city created by the dragons of Argonessen to observe the profecy in X'endrik, in other words, a anciet version of the Chamber. This could be nice 'cause you gain a free patron for your adventurers and can make some use of the Draconic Prophecy to make the Eberron flavor in this part.
4 - The Divine Engine can be as in the book, in other words, a eldritch machine, but I'd put their parts in various universities and personal colections of dragomarked heirs, so you can put a little of politics in your game. Or, if you prefer the exoteric style, make it fragments of the prophecy: dragonmarks spread in key locations of Khorvaire.
5 - Time travel should take the adventurers to Daakhan Empire, in the majestous city of Shaara't (Ancient Sharn), and put the would-be-lich there. Or, if you like megaplots, make Acererak a child still mortal version of Vol (do not recomended).
6 - Change planar travels for bizarre locations in X'endrik. It could be very nice to have Earth Giants in the desert, Icy Giants in the EverIcy, and Flamefall tower in any volcano with the tower itself being a Eldritch Machine!
7 - Change the "Three Corners Gambit" for Droam, Dargon and Breeland, so you can put a lot of political pressures typical from Eberron.
8 - Fanally, change the "Court of the Fallen Leaves" for the Undying Court if like the flavor, or mantaing it if like to put a element of Eladrin Vengence above the Giants.
That's it. I think that with this terms you can adapt the story, but yet IMO, there is a lot of work to do with the encounters. Hope I could help and good luck, ROTG is a very funny module.
I really like your suggestions. I was thinking of linking it to the giant Empire of X'endrik. I'll save your suggestions and see how to tailor it for Eberron as you suggest.
*Argent may be scrapped, a ruin in Xen'drik displaced in time, or subsituted in whole or in part for Stormreach.
*Change the main villains into Lords of Dust/their affliates. Tiamat is a Lord of Dust in Eberron, afterall.
*The city under siege in the adventure hooks can easily be Stormreach, or that Riedran city.