So, presumably, you're finding the extra 2 week by killing the rest weeks during the 6N?
You're also planning on reorganising the entire rugby calendar of every nation, but, for the purposes of this conversation (granted, there's absolutely a bigger conversation to be had) to suit the fans of English clubs who don't like losing their England players for 2-3 matches a year that clash with international training camps - most of whom dislike it because they believed false information about "no more clashes" without realising that 8&9 are bigger numbers than 6.
TBH, the moment you're relying on other nations to bend over backwards for the benefit of English domestic fans, it's failed the "acceptable" bit.
On the greater conversation, I disagree with your proposal significantly, and on a number of points. But this isn't the thread for that conversation.