Hey,
I’m using the Hope single speed hubs as they are easy to buy in the UK and a lot cheaper than the alternatives I would have to ship in from the USA. I do love the Onyx hubs especially as they have more choice on spoke count and some of the colours are yummy!
The Hope’s use a 10mm threaded bolt which is nice and long, similar to the Onyx but in stainless.
The dropouts can have a bottle cage boss brazed in if mudguards (fenders) are needed. I did this on my wife’s winter single speed commuter. I try to keep things simple.