In trying to size up this question I turned first to look at what Turkey replacements are considered viable as commercial products. A recent round-up of the top 5 retail products was composed of seitan, or vital wheat gluten constructed "meats."
Has the defined texture of turkey meat
- Properly prepared, seitan can easily mimic, though not quite replicate (it kind of "snaps" where turkey gives/tears) the tooth of turkey. A variety of preparations can be used to achieve this effect from baking in basting broth, steaming and baking, browning and baking, or boiling and smoking.
Has the moisture level of either light or dark meat
- The variety of approaches above in dealing with seitan can help to tailor the white meat taste to approximate white meat quite easily. It is more difficult to hit the nail on the head with dark meat. That said, preparing the seitan loaf as a roulade can provide some consolation to dark meat eaters.
Has the defined texture of turkey skin, whether deep-fried or baked
- In spite of my failed experiments with yuba, I have found a few additional approaches satisfactory. Recently I tried one with a puff-pastry crust that did not nail the texture, but did well to match the flavor of turkey skin. In my own kitchen, I did a bake and baste prep beforehand, and then in the hour before serving, browned the loaf in a paprika/garlic/onion-powder crust and baked on each side for fifteen minutes at 350'F.
Has the flavor compatibility to suit either a mushroom or vegan sausage stuffing Has the flavor compatibility to suit either a rosemary or vegan sausage gravy
- These two criteria are rather easy to meet for any of the vegan meat replacements as they just require that you season accordingly. I expected there to be more off-putting elements but most remained fairly compatible (even the smoked seitan).
When made from scratch, does not exceed the cost of a relatively sized bird
The commercially produced vegan variants are all about $8-10/#. If 1# of turkey yields approximately 0.4# meat; then a relative cost of $0.50-1.50/# ($1.00) translates to $2.50 per pound. The cost of seitan is approximately $3 per pound of vital wheat gluten, and $3 per pound of tofu (if you use a recipe with tofu). A seitan loaf will likely exceed the raw cost of a bird, but not by a significant amount.
Also, a serving size of seitan is 150g (per Tofurkey Feast nutritionals); the rule of thumb for turkey is 1 pound (453g) per person. Granted, it is a 1:3 ratio, but I'm not sure this is definitive evidence of cost parity as the seitan amount is a "serving recommendation" and the turkey amount is based on year-over-year consumption (though I will attest that I am less inclined, for better or worse, to go gorge on seitan).