It would seem to me that fermenting till dry with an OG adjusted for your final desired abv would be more consistent. Your first batch would probably be a little bit off, as different yeast strains will end at different FG's given the same starting mix.
Halting fermentation in cider is a little bit difficult. Yeast just loves apples. The best way to do so would probably be pasteurization rather then a chemical addition.
I find that a champagne yeast will usually have an FG of 0.98 in cider. So, if you are wanting an abv of about 7 then an OG of 1.032 would be what you would want. That works out to an abv of 6.9%.
Lots of ciders start more like 1.05 though. So you may need to either dilute, or change your abv target to be more in line with your typical cider gravity. If it was my project, I'd adjust target abv upward a bit. IMO, diluting would decrease the quality of the finished brew. At 1.05 OG you would end up with a abv of 9.3 with an FG of 0.98.
With the first batch, I'd back-sweeten to taste. Then take a gravity reading, and back-sweeten the whole batch to match the gravity of the sweetened sample. The next batch could then be back-sweetened to the same increase in gravity. Here's a thread on calculating gravity increase based on lb's of sugar added. http://www.homebrewtalk.com/f14/how-...itions-249672/
For a cider with a target abv of less then 10% I doubt you would need to add any nutrients. Though, I would add pectin enzyme. Depending on the apples, pectin can represent a fair portion of the OG. If you don't break up that carbohydrate into sugar so the yeast can eat it, your FG is going to be inconsistent. That is, if you ferment until dry. If you halt fermentation, then you may have an inconsistent sugar content. That's really only a problem with apples harvested at different times, or in different years though.
FYI: You actually can use dropped fruits to make cider. They need to be cleaned, trimmed, cored, and cooked though.
Hmm. Not sure if this post is going to end up being helpful or confusing...