Agree contenteditable is not implemented consistently across the browsers and with Aloha Editor we try to reduce that pain... Did you test the most recent paste plugin? https://github.com/alohaeditor/Aloha-Plugin-Paste/tree/maste....
This plugin provides a methode to register paste handlers the clean the pasted content. Imho the MS word copy/paste should work quiet good in most cases. Unfortunately there are only few other handlers implemented yet, so coping HTML may remain unhandled...
