Why anyone would want to complicate maintenance or troubleshooting on a bicycle that ostensibly could be 100 miles or more from a LBS or a good box of tools is beyond me. No custom builder will do it as you wish because they know they will end up eating it and getting trashed on a forum somewhere.

That rant out of the way, In the olden days before wireless cycle computers you would occasionally see the computer wire routed through the fork blades by slightly enlarging the weep hole on the bottom of the fork blade and drilling a matching hole through the top of the fork crown and then routing the wire up the head tube to the computer.

With a uni-crown fork you can drill a hole through the steerer tube to the inside cavity of the fork blade then bring your wire up through the steerer. The stem won't be in your way but the star nut will need some slotting and you need to drill a hole through the stem cap. Wire to the head light. To the tail light you would need to braze in a internal cable setup through the top tube to route the wire back to a tail light. Again the likely hood you would find someone to do that for you is pretty slim.