Sheet bracing on weatherboard extension

you will have to pack the other parts of the bracing wall out with strips of similar thickness material, seeing it is a weatherboard clad structure I would be trying to replace the plywood bracing with type "B" strap iron bracing units with equal racking resistance because packing the walls out could cause problems with reveal widths changing.
regards inter

When doing weatherboards we brace the entire length of the wall which has been stipuated to be braced, this way the entire wall is set out the thickness of the ply and we dont have to worry about packing ont the bits which were not required, Ply is cheap so unless your walls are extreemly long then the aditional cost is not much, and the extra time it takes to cut stris and pack out the extra bits of wall will be offset by the extra cost of a few sheets of ply.

For the reveals, just order the particular windows in the braced walls with an additional 5mm reveal to account for the ply.

Thanks for the help guys. Most appreciated!

On a similar note, does the wall wrap go in front of the plywood bracing (between weatherboards and plywood) or behind it?

Foil Wrap goes after the bracing, the idea is to create a moisture barrier between the frame and final substrate (bracing would be considered part of the frame), be sure to get a breathable type for the walls.