Is this road/city frankenbike concept a feasible idea? I do a half-hour each way city commute every day and the Yepp EasyFit mount I just installed on the rear rack of my already over-optioned Vanmoof 5.1 is the straw that broke the camel's back. In addition to the front carrier, integrated chain and SRAM Automatix hub it's just too heavy. I can barely lift the thing.

I need a lighter bike.

But I do like some of the features of the Vanmoof:


Un-stealable, always charged, ridiculously bright, hub dynamo powered lights
Rust-free, "natural" don't-care-if-it-gets-scratched aluminium frame
The lock integrated into the top tube—easy and quick to lock and unlock, even wearing thick gloves
Low-maintenance straight chainline (I detest  derailleurs)
Dutch-style upright riding position
Mudguards and chain guard–I ride to work on the thing and I'm not interested in changing clothes to ride


I'm tossing around the idea of building up a custom city bike, starting with something like a Surly cyclocross frame and a NuVinci rear hub (I have one on a bakfiets and love it), with the Yepp Easyfit rear rack on the back and some kind of basket on the front. Add mudguards and some kind of lighting system and I have a bike that's light and fast when I want it to be but still capable of doing the preschool or shopping run.


Is this remotely feasible?
Any recommendations on hub-dynamo powered lights and how to mount them to this kind of frame? 
What do I do about locking the thing and retaining at least some of the advantages of the built-in lock on the Vanmoof?
What kind of brake system might be appropriate, and compatible with the NuVinci on this type of frame?
Tyre recommendations (Thickslicks be good?)
Are there any non-janky mudguards and chain guards that will fit this setup?
I think your idea is sound, a lighter alloy frame, with decent tyre clearances to allow the comfier larger tyres.


Hub dynamos go in the front of any standard wheel.  There's nothing particularly special, as long as the axle mounts suit the frame's fork.  That's probably nuts and bolts, rather than a QR or other quick removable fastening.  Also wires - you'll probably end up with externally routed power cables because internally routed ones would be hard to retrofit.
Lock - I am unfamiliar with the lock, but based on this image its just a chain in a tube that is fastened to the bike permanently, but offers no protection to the wheels.  Its an abus lock, just buy one of similar size and carry it in your basket.





Brakes - you'll need two independent brakes, one on each wheel.  Whether you go disk or caliper or canti or V brake will depend totally on what mounting bosses are on your frame.  That will dictate whether your wheels need a brake track or a rotor mount.  A CX frame will probably be cantilevers unless its from the last couple years.
Tyres - thickslicks are susceptible to punctures.  I have a lightly set laying around and haven't found someone I hate yet to off-load them to.  Based on the lock pic, the default tyres are fairly large.  You want to keep that sizing or similar.
Chainguards - ugly things.  Consider a belt drive instead, which will be a fair match for your IGH.
Mudguards/fenders - they're all a bit large, because they have to sit close to the tyre and cover at least as wide as the tyre.  Mudguards also should go quite low behind both wheel, so you're stuck with at least 1/4 to 1/3 of the circumference on the front, and a bit over 1/2 a circumference on the back.  




Alternative idea #1   Since you like basically everything about the vanmoof, consider checking their current lineup for a model more to your current requirements.    Their website doesn't list weights, but some resellers might.

Alternative idea #2   Strip the usable bits off your current bike and fit them to a replacement frame that suits you.    Its an option, but I'd suggest your existing bike has a value and can be sold on to fund the new one.