Well, first I'll note the problem - tower dives 3+ v 1 bot lane. Ranged champions are squishy and frequently have no CC or escape-ability. If you've watched worlds at all, it's relatively easy for a 3 or 4 man gank against a lane-swapped tanky top laner to result in a free kill under tower. That's a tanky champion who has hard CC - now consider an ADC or other ranged champion who might be able to CS in a 1v2 lane and realize they're going to be easily tower-dove.
Anyways, to answer your question:
Caitlyn is excellent because she outranges everyone and her Q goes through units. She can do a pretty reasonable job of cs'ing safely so long as she doesn't get dove. She does have her traps and net to try to help her out under tower as well.
Varus lacks the CC but has a very long range ability to farm with.
Vladimir has good sustain and can pool if someone tries to dive him.
You might also consider a long-range mage with good waveclear - Lux, Xerath, Ziggs, etc...