Hmm - I tend to think that, for AD carries to be viable in a solo lane, they should give something up. Meaning, they need to trade part of their late-game strength for early strength. Plus, solo lane AD carries need to have a way to benefit of them getting solo experience. Let's look at prominent examples:
Top lane. Benefits from XP by means of her passive (an important part of her damage), independant of her skill order. Also, has multiple ways to deal with being alone in a long lane (good base MS, good base stat tankiness, Blind, Gap-opener). Trade-offs include sub-standard range, a factor of unreliability, and lack of teamfight strength.
Mid lane. His abilities, combined with Trinity Force, give him good mid-game damage, poke for sieging and a good enough laning phase. Again, his trade-offs lie in the reduced late-game effectiveness due to low base AS and low AS scaling.
Mid lane. Same vein as Corki, with a bigger emphasis on single-target damage.
Also, two other carries that shouldn't be too bad in top lane, at least against melee champions:
Tankiness, Escape, punishes melees for getting close. His sole problems are his rather exorbitant mana costs. Maybe, after the changes he's possibly getting, better for toplane.
Tons of range, as well as two forms of disengage. In theory, leaving her top-lane, out of the action in the lower parts of the map, should allow her to mitigate her mid-game hole. Also, her passive benefits extremely from solo lane XP.