I like that retaining wall. A raised flower bed. Nice touch. I also like the landscaping done on right side of photo. In short, i'm liking everything about the 'after' photo

May I suggest that you look up the NCC Volume 2 which specifies the safety design parameters for stairs and balustrades. Any new work done on stairs and balustrades must comply with the code. You need to look up sections 3.9.1 and 3.9.2 In summary, whatever method you look to you can't be able to pass a 125mm sphere through any part of the stair or balustrade. It also specifies the design parameters for wire balustrades to achieve the 125mm sphere rule. The design challenges for stairs are significant if you want the open back tread look. The easiest way is to install a block on the underside of the tread level with the back edge of the tread below. This way you can still have an open tread and achieve compliance. The harder problem occurs when using a wire balustrade and the resolving the gap that occurs between the treads and the lowest wire. I have seen several installations of late where the 125mm rule was very clearly not achieved. One was a very recent build and I'm still not sure how it passed the final inspection. The images from Miami Stainless show how this can be achieved. Clearly the best and most secure is the glass balustrade and the vertical bar balustrade. Good luck!

Here's the original discussion ([https://www.houzz.com.au/discussions/help-with-stairs-dsvw-vd~5209387[(https://www.houzz.com.au/discussions/help-with-stairs-dsvw-vd~5209387)) for context.

Go for option C, possibly with a dark timber for contrast and drama. If it is slightly different it will look slightly off and annoy you forever. However I would be asking the question "why it is not available for stairs?". Stair treads get heavy use so you need a durable timber. If there is a question over the durability of Whian Whian Blackbutt for stair treads then maybe you should reconsider it for the rest of your floor? Best of luck, Dr Retro of Dr Retro House Calls