Electroless nickel plating is the least corroive method of the lot. But phosphorus and steel are incompatible - and electorless nickel co-deposits between 2 and 6 percent phosphorus.
The assertion that nickel plating is nothing but good is false if it's going down on a normal low alloy steel. Nickel is less reactive than most steels, including activated stainless steels. While it's not a point of failure (generally) is car parts or aircraft parts, it's also not usual to find said parts up to their bottom bracket in mud full of grit.
From a total cost point-of-view, the cheapest method for maintaining corrosion resistance in 953 is to source the right filler wire (the nice thing about the alloy that 953 is made from is that it's a very low carbon steel in the first place, so any C455 wire will be acceptable to fill with, you don't have to source a special filler wire), and then have the assembled frame passivated in a 50% nitric acid bath.