If you are going to use these year after year, and are set on using wood, why not make them of pressure treated pine? In the long run these will last years and years. The ones I used to build were about 14' to the platform, weighed a bunch, were stout and attached to the tree with a ratchet strap or chain tightened with a turn buckle. Some of these are still out where I used to hunt. Good buddy of mine stillm huints there. These stands ahve been out 20+ years old and are as stout as ever.
I have not built one is aboutt 6-7 years now, and am not sure what the materials would cost these days. If you want the plans I probably can find them. Nothing more than a wooden ladder with a platform at the top.