(Let me prefix this by noting that Allan is surely already aware of the requests for native SFTP, version control UI integration, and other things mentioned in this thread, because he's said so -- in some cases multiple times -- on this very mailing list.)
Here, access to svn is *very* close at hand. I don't see the benefit of expending energy to writing a "built-in" svn client when access to an *existing* client
Try this: In TM's project drawer, in a project checked into Subversion, rename any file.
Result: you've just broken your Subversion working copy, because Subversion was not consulted about the name change. Renaming the file back will fix it, of course, but you get the idea. That's the level of integration we're missing: the 'oh, TextMate *understands* Subversion' experience, as opposed to 'TextMate supports Subversion' (or Xcode's wacky 'dude, where's my SCM status?' shell game). It requires a level of plugin support TextMate doesn't provide yet.
To be clear, I am _not_ criticizing TextMate's development history. Quite the opposite: I'm happy with where TM is and where it seems to be headed. Well-architected code takes time. If TM already had some of the features under discussion here, there'd be other features missing that are more central to TM's mission, like, say, snippets.
Bottom line: the SVN bundle is not shabby at all, but there is certainly more that could be done to *integrate* Subversion (or CVS, or Mercurial,...), given future potential support from the TM core app. (There are also more commands to be implemented, but that's another thread...)
Chris (creator/co-author of the Subversion bundle)