If you plan on doing pieces of a trail, 1 week at a time, realistically set a goal as to how many days of that week you plan on actually hiking, then how many miles you would like to have as a goal for each day. Having the mileage you would expect to complete, days hiking per trip, and miles per day would help with this.
As far as that goes, there are numerous trips you can plan in between the stretch of the end of the Smokies, up until you get into Virginia. I remember this part of the trail being somewhat challenging at times, but those challenging parts were rewarded with amazing views or a couple of days of relief after a strenuous day. Gorgeous section, especially in the late spring/early summer when everything is in full bloom.
One person mentioned Standing Bear Farm as a good place to jump on/off from - here is their web page:
http://standingbearfarm.tripod.com/
Here is another list of shuttles along the trail that can help you get to and from as well:
http://www.appalachiantrail.org/atf/cf/{B8A229E6-1CDC-41B7-A615-2D5911950E45}/AT%20Shuttle%20List%20WEB%208-17-10.pdf
Have a great time!
bearbait