MIMF

I am gathering materials for my next guitar build. So far I have hard maple for the neck, soft maple for the carved top (Les Paul style), and katalox for the fingerboard. I am planning to build it as a neck-through, with the hard maple neck laminations acting much like the maple center block in an ES-330.
I cannot decide what wood to use for the "wings" that will attach to the neck. My plan is to heavily chamber them. The chambers and the neck "block" will then be covered by the carved maple top. From the back the neck laminations/block will be visible.

Sitka spruce looks similar to maple and it's not very expensive in the size I need. Would it be a good candidate for this? Is it durable enough to take some hard knocks? Or should I stick with mahogany or walnut?

I want something lighter than maple, hard enough to resist damage (no basswood!), and that will look good next to the maple that will run through the body when viewed from behind. And it has to take stain well. Any suggestions?

Spruce does not fit your requirements well. Poplar does, however.

I have considered poplar, but I don't really know enough about it to know if what I'm getting is any good? I gather there are a lot of varieties, or a lot of woods that are called poplar?

This discussion reminds me of Les Paul's "the Log" that he put together as a beam (through neck) with archtop guitar body attached to the sides to make it look like a guitar. I see no reason why spruce would not work as added on 'wings' to the through neck, and it is lighter than maple or 'poplar'.

Have you considered the over all balance of the instrument? Some people complain of 'neck heavy' instruments.

I've crossed spruce off of the list of possibilities.

I have considered balance. I'm hoping it won't be too bad, but I played an SG Special for years and my current hollowbody also neck dives so I'm used to it.
I'm planning to use a Bigsby or a heavy tailpiece and I'm hoping that will help a bit.