I agree with john there isnt any need for a v brake on a bmx if you get a well set up u brake some decent pads your brake will work amazingly, remember this isnt trials so you dont need a brake with instant lock alot of new comers from trials dont realise this, youll need a brake with nice modulation.
Personally id steer clear of the profile cranks there good but i think there are better cranks out there like my primo exels awsome cranks.
What you said about lever ratios, i had a play and tryd to use my avid ultimate lever with my fly brake and lets just say it didnt work at all. A dirty harry lever and evolver brake will do you proud