No, it kills me to read this thread, since I really want one. But justifying it is just impossible - the roads are maintained, and though it could be better, I've found that a combination of front harley rake and rear landscape rake does a really good job. And I have those, so really tough to justify a new implement.
Bfreaky, really impressive work! And your english is perfectly comprehensible, quite good. If you have not used a box blade of some sort before, keep in mind what mtnview said, they can easily stop even big strong heavy tractors. I like your plans, but I worry they might be too big.