I think it is ridiculous to even suggest that the National Guard should have a separate presence on the Joint Chiefs of Staff. And I say that as a former Guard member who values the contribution of the Guard and Reserve components. What's next? Adding Reserve component generals? State defense forces? Homeland Security Secretary?
The top Air and Army National Guard generals can make the views of their Guard components known through their service chain of command. And I'm sure that the governors and state Congressional delegations are capable of making the case for funding questions from the state perspective just as well.
The Joint Chiefs of Staff is supposed to provide authoritative military advice to the president--not be a debate forum for every organization in the Department of Defense.