multidomain, multilanguage, keep indicization, multiheadache
One way to would be to build this with domain access use a different domain for each language to meet your criteria. Repoint the old urls to the new ones. 

Another way would be by indicating the language in the url.  Read more about it here: http://indico.cern.ch/event/216222/contribution/10/attachments/345315/481614/multilingual-training.pdf Start at page 37.

Probably a few other ways.