I've always built my own anchor winches, and have built them for friends, who have given up on the commercially made ones, after serious corrosion from their mixing an aluminium housing with a bronze gypsy, and a stainless shaft with mild steel keys ,aluminium drum, etc etc. None of mine has ever failed, in decades of use. I use all stainless, a wide open design, with no hidden parts.
Friends who spent a winter in the South Pacific, said they never met anyone down there who didn't have problems with commercially made anchor winches. You are far better off to weld up your own anchor winch. You'd get a far better product.
Are the plans in your books? I had to abandon the wood-stove idea for my boat(insurance :-()
The Anchorlift winch is my first choice right now, there's a choice of all aluminium, or stainless. Building my own, or getting one made by a person I can actually talk to has a lot of appeal.
Anchorlift USA Dolphin Windlass with Capstan- Stainless from Wholesale Marine
Is one I was looking at, I've seen them as low as 660$ on ebay.
That doesn't leave a lot of room for cost savings in building my own IMO.
So I would look at building one from the idea of making a better one(like Brent's) vs making one for less, which usually doesn't work out as well as planned.