As soon as I shoot out the barrel I have on my 204 now, I am going to go this route.
I don't like the cavernous throat on the factory barrels so I will get a custom reamer built so a 39 Sierra or 40 gr. Berger will sit in the case where it is supposed to and have a few thousands free bore. I will spec the barrel so it will finish around 28 like yours, and have a shank that will allow me to cut an inch off and rechamber when it gets throated by use. With the cost of premium barrels and having to wait so long for them, it seems to make sense to set yourself up in a way to use the entire life possible in the barrel. I have more than several Kriegers and I am sure you will like yours.
In the scheme of things, the cost of the custom reamer is low compared to the other components.
BTW, 1-12 is the limit for 39-40 gr. bullets. Sierra BK and Bergers are stabilizing in most 1-12 barrels, but you will not be able to go above that with any dependability. In my opinion the 40 gr. Berger is one of the best bullets in the 204. It is more accurate than the 39 at distances, at least in my gun. I shoot both at pds, and up to 250 yds it is hard to tell them apart. Out a ways, the Berger is more accurate in my rifle. It has a little tougher jacket than the BK if you want to go for coyote.
Sounds like a good build to me.