Hi! You must have in mind that dropouts are for 14mm axle (BMX standard), but hub spacing is 135mm (MTB standard), so single speed hub is way to go. (Fireeye had dropout tensoners that converted dropouts from 14 to 10mm. If you can find it, you can put some lighter hub like hope, dartmor razor, ns rotary, etc..) Only single speed with that dimensions (14x135) is Fireeye 1214. That hub, new, comes with 16 and 18 tooth sprocket. Hub is bombproof. If I were you, I would try to find fireeye US to Euro bb converter so that you can install any normal cranks with normal chainring. Choose the lightest cranks that you can, something like shimano slx (I had Shimano Hone). Bottom bracket comes with cranks usualy, if not, just take factory one. Frame is heavy, so you have to shave some weight on parts.