Rear derailleurs should have the same pull (except 10 speed mountain bike derailleurs) and allow indexed shifting with either sort of shifter. I'm not sure if there is a retroshift lever that will accommodate v-brakes, but I haven't looked into that. Another option (also not cheap) is Kelly Take Offs. As with the retroshifts, they would require to to find a down tube shifter set of your desired number of indexes, but work with any brake lever of your choice. I've used this setup and found it worked well enough for shifting fro the tops, ramps and hoods, but, like you say not the drops. I think it was a little easier than bar end shifting would be as I didn't have to move my hands unless I was in the drops, but there is a cost penalty of doing that. For a similar price though, you could probably just get some cheap cantilevers, a road compatible front derailleur and some 9 speed microshift levers that generally get high reviews and have integrated levers. Haven't priced those out lately, but it seems those were once in the $100 range if memory serves.