yes yes it's spotted gum lol...I haven't even been upstairs yet to see it as there are still no stairs..and I'm too afraid of heights to climb a ladder...so only seen it in photos :) Walls to be Natural White

Hi why don't you install the spotted gum floor on the staircase? you can just order a plain staircase from the stair company, and the flooring installer is able to lay spotted gum floor on the staircase. The stair nosing can be customized by using the same spotted gum floorboards. That way you will have a flush finish through the house space.

Hi Badobbs Structafloor will only span 600mm unsupported in the 22mm and 450mm in the 19mm version so no, it alone won't fix your issue. A simple fix would be to pull up the floor in the affected area and then 'pack' it up to level, THEN lay some structaflor over the new supported sub floor. This is done by getting a laser level and marking out the low points in the joists then making up packers to suit, or installing a packer and planing it down to suit. It depends on the level of dipping. It will be your cheapest option and definitely a job for your carpenter (unless you're handy). Regarding disturbing the floorboards that is nonsense. If there are other issues such as other sagging floorboards then you can address them at the same time, or fix them down properly with screws. I suspect that the real issue is that the wall removal did not take into account that the floor joists are usually fixed to it and they are now unsupported. If you get under there and find issues with your joists/bearers then it is not a big deal to install a couple of stumps/connect bearers to support them whilst it is open. We do it all the time. Either way laying a new floor over a subfloor without addressing it would be a waste of money and will degrade your new floor. Cheers

We had a pole house with timber floors around the pole. The builder did a fantastic job and recessed the floor timbers slightly into the pole, so there was never gap. Furnishing around the poles can be interesting - indoor plants are great - but realistically, your focus will be on the outside views during the day, and it will only be nights that you will think about the poles/inside :) I would probably put a couch on the view side of the pole facing the views, with plants this side - and no-one will really notice the carpet.