Actually, that is what I have been going for as well. I do like Woodchuck's dry cider but the best I ever had was from a small brewery in Colorado (long time ago) that was semi-sweet and lightly carbonated.
I have been running batches with different amounts of starting sugar (higher and lower OG's) and both Ale and Champagne yeast (still waiting on the cider yeast). I am going to divide my gallons into three different bottled batches. One will be primed with sugar, one will be sweetened with a tbsp of apple juice concentrate per bottle (or fresh juice . . . haven't decided yet) and the last will be left just to age as is.
That should give me nine different combinations to test (and I may do another if the wife isn't looking).
I will be sure to post my results after they have aged a bit. I know, it is a tough job but I really want to do it . .
My understanding is, if you want a semi-sweet cider it is best to use around 1 lb of sugar to a gallon with either an Ale yeast or a cider yeast. Then, when it is done fermenting, add some more juice for flavoring (I haven't been able to find how much).
I hope this helps. Good luck with your cider. By the way, the Crappleberry (what I have decided to call it) is going like gang busters and has a great apple smell with a trace of raspberry!