I am try to get a full list of a user's tweets. I do not particularly care what order they come in, but I need all of them, including what the user has ReTweeted. Essentially, I would like to have status/retweeted_by_me, but for specified user.
Is this at all possible?
Nope. Twitter's API leaves a lot to be desired (especially in terms of actual RESTfulness), but this particular issue is also my biggest gripe with it. You can only get your own retweets, but not the retweets of others. Look at any Desktop Twitter client, and compare a user's timeline in there with the actual timeline on the web. The latter contains all the retweets. This has been a big problem ever since they introduced the new retweets, and in my opinion is one of the reasons why acceptance of new-style RTs is slower than it could be among Twitter users. I've tried to make @twitterapi aware of the issue but never got a reply; maybe you (and anyone reading this) could do the same thing.
Their argument regarding BC is, of course, utter nonsense. It does not break BC at all, since these retweets never showed up in the first place. And even if they did, a ?retweets=true query argument would be enough to fix that. I really have no clue why they're not implementing this; their own website shows the retweets fine already, they just need to expose it in the API.
This was addressed recently by the Twitter devs. You can now add a include_rts=true to your call to user_timeline. See the full discussion here: http://groups.google.com/group/twitter-development-talk/browse_thread/thread/7a4be385ff549ed0