1. Bruma should have a completely different set of buildings from the way they were during Oblivion since those buildings would have rotted and fallen over a while ago and new ones would have been built in their places, with the exception of the chapel and castle which were made of stone and would still be standing but more worn that in Oblivion. The chapel would likely be closed down though since talos worship is banned
2. Cheydinhall wouldn't have changed to much in my opinion except it would probably have grown quite a bit since allot of the refugees from Morrowind probably would have gone there and it would most likely have a slum now since the refugees wouldn't have much money.
3. Chorrol would have changed the least since i don’t think it was involved in the war except for holding imperial troops before the battle of the red ring road.
5. Kvatch is rebuilt by now but it would have been conquered by the thalmor so it should have a strong thalmor presence and probably be rebuilt out of stone to avoid getting destroyed again.
6. Skingrad would probably not have changed much except for some damage since it was attacked by the thalmor but it should have already been repaired and Count Hasildor would have probably been replaced with a thalmor agent when the city was taken but he would still have a high ranking position.
7. Anvil would probably have grown quite a bit since that would be where all the thalmor ships would dock when heading into Cyrodiil but it would probably have had allot of changes to the original buildings since it was also captured by the thalmor.
8. Bravil is probably mostly a ruin with collapsed buildings everywhere and huge portions of its walls gone since it was in bad shape during oblivion and it was a major battle ground in the great war. i think it would probably like an elaborate maze of rubble and buildings that are halfway sunk into the Niben.
9. Leyawin probably drastically changed since it is now owned by kajhiit and was attacked allot during the war. Now it would probably contain a few old buildings but it would likely have allot of kajhiit style buildings since they would have been the ones to rebuild it.
10. The Imperial City would not have changed too much but it would have a lot of battle scars and a huge thalmor presence. The thalmor probably would have taken over the talos plaza and used it as their headquarters in the city and the thalmor would probably hold a section of the imperial prison and about half of the palace. I’m also assuming that the waterfront would have a ton more people living there since allot of residents would have lost their homes to thalmor agents. The Arena would probably be pretty different and be owned by the thalmor now since it generates allot of revenue. The elder council probably is half way controlled by the thalmor too. The thieves’ guild is probably living in the sewers now along with allot of other people who the thalmor would want dead, such as ex-blades, rebels ex-elder council members, and anyone else with power to challenge the thalmor. The arcane university is probably under thalmor control as well.the imperial city temple district was destroyed during the oblivion crisis so we might have to rebuild that unless the thalmor already did but if they didn't we should probably stick to the original structure but of course with better graphics
11. Cloudruler is probably burned to the ground but there might be a secret vault or something beneath it where the blades hid most of their treasures before they were killed. It would probably contain the armor of tiber septim, old blade armors all the weapons recovered by the champion of Cyrodiil, and his imperial dragon armor.
12. The wilderness probably would not have changed all too much although the oblivion gates after the great war were permanently left there without the portal.
13. The people are likely to be allot more worried and tired looking with the constant stress of war.
14. The guilds would still be functioning but would be monitored by thalmor at all times.
15. The Main Quest should revolve around a Rebellion against thalmor rule by Imperials who have lost their homes and families. The rebellion should be a quiet and more stealth full battle than the Stormcloacks and should focus more on a small group of about 100 or so men who don’t fight the Empire and are solely trying to remove the thalmor from Cyrodiil without causing a full scale war that would destroy the Empire. I think the quests should deal with stuff like infiltrating thalmor areas to steal documents and assassinate important thalmor figures. The quest line should conclude with a battle against a thalmor stronghold where the aldmeri dominions leader is staying, but unfortunately the majority of the rebels are killed in the assault while a small group of the rebel leaders attempt, and fail, to assassinate the aldmeri dominion leader which ends in the rebel leader being killed and telling the player to lead the remnants of the rebels away to fight another day, at which point you have to escape the stronghold and return to the rebel base which is now yours.
16. The rebels should be very stealth oriented and wear disguises while on missions. For example, while on an assassination mission the rebels dress like the dark brotherhood to attempt to hide their identities and they dress ass thieves’ guild members while stealing from the thalmor and they dress like bandits when ambushing thalmor troops. They should always maintain a low profile and the thalmor would keep the attack on their leader a secret to prevent more rebels from attacking them. (This also keeps the mod from hurting any of the lore in future games since no records would be kept of the rebellion and it would be like it never happened so it would make sense that it was not mentioned in future games.)
In response to Deamonata:
It was stated in Skyrim that Kvatch was in the great war but was taken over by Thalmor so it was clearley rebuilt.
Skingrad was also taken over by the Thalmor during the war so it would either have a Thalmor leader now or a Thalmor advisor to the count.
Whitegold Tower was burned as were allot of other parts in the city, but the city is made of stone so i doubt it would have left much of a lasting impact besides maybe a few scorch marks (Whitegold is obviously still standing since it is in Skyrim and it has lived through thousands of years and a few battles.)
Where did you hear that the mages guild was destroyed?
The Dark Brotherhood is only surviving in Skyrim, it says so during its quest line.
A Response by Deamonata
1. I see Bruma as becoming militarised due to the war the count is now longer in charge. I agree the chapel would likely be closed down though since talos worship is banned
2. Agreed
3. Agreed
5. I don't think kvatch would have been rebuilt, too many deaths occoured there for people to realistically want to live there.
6. Count Hasildor should either still be in charge or maybe the population discovered that he was a vampire and killed him. A thalmor agent wouldn't be incharge as it is still the empire's territory.
7. Anvil would probably have grown quite a bit since that would be where all the thalmor ships would dock when heading into Cyrodiil but it would probably have had allot of changes to the original buildings since it was also captured by the thalmor.
8. Bravil is probably mostly a ruin with collapsed buildings everywhere and huge portions of its walls gone since it was in bad shape during oblivion and it was a major battle ground in the great war. i think it would probably like an elaborate maze of rubble and buildings that are halfway sunk into the Niben.
9. Leyawin probably drastically changed since it is now owned by kajhiit and was attacked allot during the war. Now it would probably contain a few old buildings but it would likely have allot of kajhiit style buildings since they would have been the ones to rebuild it.
10. The Imperial City would have undergone huge changes. it would have a lot of battle scars The waterfront would have a ton more people living there since allot of residents would have lost their homes in the wars. The white tower is now destroyed, and most of the districts were severely damaged. The arcane university is no more as the mages guild
11. Cloudruler temple I would see as being controlled by the Penitus Oculatus, but thats open to debate
12. The wilderness would be majorly unchanged but would still contain lots of signs of battles, e.g mass graves, battle grounds.
13. Agreed
14. Unsure about the guilds, the mages guild is gone and so are the blades only leaving the thieves(may be fine, certainly no thalmor influence), dark brotherhood(probably destroyed based off what I saw in skyrim), and the fighters guild (possible influenced by the thalmor)
+Twilight
12. If the Thalmor has taken the Imperial City by brute force then no city would have stood in their way. They must have taken the city in some clever way, maybe a traitor?
13. People might be happy that the fighting has stopped…
14. You gould have a more generic Assassin's guild. There may be no mages guild, but you can stll have organisations based on the schools of magic. Restoration would be in the churches as before. The Nechromancers would probably still have their organisation. Maybe some druids could come out of hiding and teach alteration & animal charms.