I'm assuming the wood siding was painted and that's the reason for residing????

Are you sure you can't have the siding scraped? Older homes than yours still have their original siding.

Super cool house, agree - can you scrape? Vinyl would sort of kill the vibe.

We've been told that some of the siding is warping and peeling away from the house due to the elements (we live in Vancouver BC and its very wet here), and the cost to repair the current wood siding would cost almost as much as residing the entire house.

Vinyl on that large of an empty field (the 'butterfly wing' on the left) will most likely show lots of waves and canning. I understand following the angle of the roof with the siding, but it usually is more successful on steeper angles. If it were me, I would be looking into alternative materials, like fibercement/Hardie, steel, or stucco (panels). I would separate the two wings visually with either horizontal and vertical lines mixed with solid. The front, and the garage (if that is what is on the other side of the swingset) I would "inadvertently" exclude from this design, just as the original designer did.

Ugh. Don't use vinyl. I put it on my house in NY and need to power wash the mildew off every two years. Our climates are sort of similar with plenty of wet humid days. Your house is very cool, but I don't really like angled siding - it was used here in the 1980's a lot and now looks very dated.

From the pics, it looks like it's hard to see the sides from the front - there is no rule that says all four sides need the same material. Hardie makes a fibercement panel system for board and batten, and this might be an interesting choice for the rear (?) wall. Good luck