The only way you could do that would be to use the Aeronaut cross body with the Absolute Strap and the Brain Bag on your back.
I use the Brain Bag domestically with a Large Cafe Bag, they are both packed really really full and even for me, somebody with a big frame, it feels like a trek to walk for some time.
You might be able to do it if you choose a Dyneema Aeronaut and pack it loosely.
You might also choose the
Camera I-O - Camera Bag. - TOM BIHN for your DSLR.
You could place it in your Aeronaut while in transit then remove it and wear it with the Absolute Strap while at your destination.
You could use a
Packing Cube Backpack (Aeronaut) - Travel Packing Cube converts to an ultralight backpack - TOM BIHN to carry the iPad, Kindle, moleskin small, tour book, wallet, and charger and walk around with it on your back and the The Camera I-O (Insert-Outsert) cross body.
I know about the bulk of the Brain Bag but I don't know anything about carrying bulky photo/video or audio equipment.
There are several members with experience in this matter, however, they are usually on the road but you might be lucky and catch one on the forum.
Hope this help!