Long term maintainability is of course a valid concern, and airgun accessories tend to incorporate hard to find or custom parts - for example there's the custom spring used in WAR's SSG, springs being a category of part known to frequently have a finite service life. However, in the FFH coupler case, a simple call to the vendor would fix you up with any of the FFH components you might need.
On top of which, of course, is the fact you could buy three complete FFH kits for the price of one SSG and keep two on the shelf for spare parts! LOL!
Meanwhile, it's interesting that you knew about WAR's SSG before you saw the FFH, considering the FFH was actually on the market first.