So here's my question: why would you replace the natural oak for Maple? They eventually look the same? Maple does NOT stain very well. If you plan to leave the Maple in a natural 'pale blond' finish you probably should know Maple turns DARKER as it ages (it's called photosensitivity). It moves from pale blonde to a STRONG yellow (just a snick lighter than your current rail).

Is there a reason for a change of wood?

The steps were carpeted, so only the wood of the railing is changing. I did the steps in maple, with the main reason being that I was having difficulty finding a oak caps in a modern style for a low price. I knew maple wouldn't stain as well as oak going into it. I'll admit it was a pain, but I got around it after trying enough types of stain. As you can see from the pic, the steps have been stained grey. I'm going to match the railing to the grey steps, which is why I'm changing the wood.

Well, if you can't find a maple in the correct colour then you can always paint the oak. I would paint the railing gray and the spindles white. It would be roughly the same amount of work as staining maple.

Might be some misunderstanding here.

I'm updating the railing and spindles to something more modern. I don't have any intention of reusing what's already there. I specifically want a modern handrail with wrought iron spindles. Which wood I use or what colour it is isn't part of the problem.

The problem is determining if I need a newel post for each change in direction if I continue to use the existing iron railing system.

What are the code requirements for your area?