I am using Classipress + WPML plugin + WPMU.
70% of the work is done.
Here is what needs to be done:
-- Make site completely multilingual (English and Arabic)
-- Right now there are problems while posting ads in categories. An ad posted in Arabic does not appear at all. (Ads posted in either language should appear under both languages)
-- Some CSS issues while site is in Arabic.
-- Some language translations ( I will provide). Maybe you need to edit the .mo, .po files.
PM me if you have any questions.
Need to start asap.