With the channel store now released, it's possible this may be added in the future -- but when, who knows? If you're looking for that solution right now, then no, you'll need to look elsewhere.
Now that drive storage is so cheap tons and tons of people are looking for the best answer. Centralized media is the future both from outside services and from within the home. The problem is converting files to a format that can be read by the current extenders and their price. Some people have been content to make the Xbox 360s work but I am holding out for something better/cheaper/easier.
Personally I wouldn't care to pay more for Netflix if they offered a bigger selection then I wouldn't have to worry with it myself. Paying for a selection that has many of my own titles plus tons more is better than paying Amazon to re-buy things I already own.