Just about "new blood"? Why is the Head of Joint Chiefs and DNI attendance now discretionary? No one said Bannon was a dummy, he seems highly driven and intelligent. I never said he didn't have a clue either---my fear is he very much has a clue but in a devious fashion. However if you don't think he is almost off the cliff at the right end of the spectrum you need to do a bit more digging...
I can try to answer this from a mil perspective. Usually at the table, when things such as national security and possible consequences that could arise militarily across the oceans, you want to have someone who is a subject matter expert that can fill you in on the pros/cons of your ideas. Military has plenty of civilian oversight but even then, those guys do take the advice of the service chiefs and the combatant commanders or shun them if they don't fit the administrations objectives (see Shinseski; who was right all along & Rumsfield is a perfect example). This type of setup will only lead to only certain pieces of vital command recommendations in reference to boots on the ground, phase IV planning, strategies, etc. being completely left out of the conversation. The only voice of the military will be that of Mattis who, as smart as he is militarily, may not be cut out for this type of shyt. He will speak his mind and that may cause him quitting or getting fired if he doesn't toe the company line