@nr 4: Though I am in favour of more communication between projects and exchange of ideas and data where guidelines differ, I am not sure about cherry-picking for translation. Simply having copies of the big projects (especially wp-en) everywhere reduces diversity. However I have to admit that I often translate content myself. Another point of concern is that the discussion about the content will become fragmented once a translation is made. There will then potentially be two groups of expert users discussing separately at different projects. For the quality it would be better to have groups of experts discuss matters at one place, for example at the metawiki. Another problem is that not all projects want a quality rating system. The Dutch Wikipedia recently voted to delete the project page on quality rating and forbid the rating of articles, even on TPs.
@nr 5: I totally agree. FR is potentially a way to increase the quality of content, and I've always been (cautiously) in favour of its implementation. Yet its effect on quality should be known better before we can draw a conclusion, since there are some potentially negative effects (what is its effect on the influx of new users for example?). Flagged revisions can be implemented in many different ways. There are some other similar systems too, like patrolled revisions, which is used at wp-nl a couple of years now, or the systems used at external projects like Citizendium. It's not simply a choice between two options, there's a whole spectrum of systems available.
@nr 6a: If FR is used, edits of problematic users can simply not be flagged as trusted.
In my opinion, translating all content is stupid. On the other hand, there is some content which is clearly project-specific. For instance, I recently needed to create an article on the history of Georgia (US state). The obvious route I have chosen was to translate an English article first, and then to add the content I find in addition. I think it is kind of obvious that articles on en.wp on the history of US are of good quality. As another example, articles on Paris metro stations on fr.wp are not fantastic, but they are still a good basis to improve on after the translation; on the other hand, en.wp articles on the same topics are often substandard and not really recommended for translation in other projects.