It may be to late now to reply to you.. but if other SEA players out there can read this reply of mine.. with a ping of 50-100ms in game,, it will probably help them how to have english settings in Aion TW which is chinese.
NOT SO GOOD METHOD BUT IT WORKS:
1. NEED AION NA File (version 5.1/5.2/5.3 etc as of the date of posting)
2. AION NA File Folder > find L10N/ENU/copy the files here (use to have the english language in game) EXCEPT FOR "enu.dat"
example: Aion NA/L10N/ENU/will have these files inside in it
data (folder)
sounds (folder)
texture (folder)
enu.dat (<=DO NOT COPY THIS FILE)
3. GO TO YOUR AION TW File Folder > find L10N/CHT/backup the files here (chinese language in game) EXCEPT FOR "CHT.dat"
example: AionTW/L10N/CHT/will have this files inside in it:
data (rename this to data-orig)
Sounds (rename this to Sounds-orig)
Texture (rename this to Texture-orig)
CHT.dat (<=DO NOT CHANGE THIS or DO NOT DELETE)
4. PASTE the AionNA/L10N/ENU files you copied into the AionTW/L10N/CHT/(paste here)
5. Start AionTW and see if it works.
If you dont have Aion L10N files for the current version.. you have to probably ask for a friend to upload it for you..
My system config: Windows10 64-bit