I believe a lot if not all of the content from 3.5 should be included.
Changes:
Erenor needs to be nerfed, Either by how much it costs to make or the DPS and stats it provides. I say this because there is a lot of p2w (pay to win) players, BUT there is a large amount of players that are Free to Play, If the free to play players are running around and getting dropped from the people with good Erenor weapons/armor they will get extremely upset/bored of the game and will want to quit which is obviously not what you want.
The trading system in my opinion was really good, people could do land runs and sea runs, i like sea runs more because the rewards is more but there is a chance you run into pirates, which brings a nice balance of PvE and PvP aspect for trade runs. Maybe keep the land run system the same but add something in todo with the 3.5 system.
The Erenor cloak is fine, since that does not give insane stats like the Erenor weapons, also brings in a nice PvP/PvE aspect to farm the materials from the new areas, also the scroll that is needed to make erenor is a tradeable item so people that want to farm it and sell it to make a gold is nice!
The new area brings in a another event like CR/GR rift (forgot the name of it) which is always a bonus for players looking to PvE and farm honor.
Ancestral skill is a big YES in my eyes, it brings in more fun for PvP side of the game and another farming thing to keep people active.
I think i have mentioned the big aspects of 3.5, all the minor things that are added i personally agree with.
Personally thing id love to see is the:
Transmuter: Transmuters can now be used to choose which item subtype you would like by re-cloaking the item. Cloaked items do not lose their grade, and are also required in upgrade crafting.
Thank you and hope this feedback helps