I have seen a few M1 rifles "sporterized" much as you describe. Some were essentially the same idea as "tankers" except with a slightly longer barrel and a sporter stock. One I saw had a nice checkered walnut stock with a high comb, rear sight removed, an offset scope, and the gas piston inletted into the fore end. Polished and blued, it was a nice job. I forget what the price was, but it sat at a dealer's for a couple of years, and was still there when he went out of business. I don't know what happened to it.
As to converting to straight pull rifles, it is pretty common in states where semi-autos are not legal for hunting.
Jim