LiefLayer: Just grab the old cider wrapper here:
http://portingteam.com/files/file/7163-dragon-age-origins-steam-version/

install the game on a windows virtual machine and configure it with the settings you want (screen resolution etc...)
copy the Bioware/Dragon Age folder from Documents folder on windows to Documents folder on mac.
copy the game folder inside Program Files folder in the wrapper
rename the folder from Dragon Age Origins to dragon age
change the Info.plist file inside the wrapper from
c:\Program Files/Dragon Age/bin_ship/revloader.exe
to
c:\Program Files/Dragon Age/bin_ship/DAOrigins.exe

if you need any help just ask me.

I think (not 100% sure) that the portingteam port is the old cider official port from the retail version.
Also I played the base game with it without any problems.

PS. remember that if you want to use wine on mac (this is not the case) you just need to use wineskin instead of plain wine... and that portingkit app and portingteam website contain many premade wrappers.

PS2. Also there is a crack inside the portingteam wrapper, but you don't actually need it with the gog version.
Just remember that what you download from portingteam are just wrapper (not games) and to make steam version work sometimes they include crack (the steam client port is a recent thing).

LiefLayer: sure, it is really easy you just need to go to:
~/Documents/Bioware/Dragon Age/Settings

open DragonAge.ini with a text editor
change
[GameOptions]
Locale=it-it
VOLanguage=en-us

to your language

(example
Locale=de-de
VOLanguage=de-de
since you are from germany you can change the voice over too).

gog version should have all the language in one package.