- Wear your shoes on the plane. The added value of a change of shoes is small, and the weight and space savings is considerable. Besides, you'll need comfortable shoes appropriate for wear with a suit anyway. If you'll actually have time to work out at your destination (good for the nerves) look at the recent sneaker thread. Lifting weights in good shoes in a hotel gym is also not unheard of.
- If you do indeed need two jackets for your trip, travel in one. It's easy to lay on top of a bag in the overhead, and it means you have less space.
- You can easily fit all that you describe in a carry on like the ebags motherlode convertible. See the learn to fold a suit thread. Never a problem to fit, even on regional jets. I just took mine to a conference and the first night at dinner, when it was clear I had come straight from the airport, I got asked "Where's your bag?" It was assumed I just had a large briefcase with me.
- If you can, go even smaller. With a 15" shirt folder, I easily traveled for 1 or 2 nights in nothing but my standard messenger bag and a very small duffel (18"x9" round?) for similar interviews. Getting the to plane late never mattered - even when the overheads were already "totally full," I could find a place to squeeze it.
- Plan to be overdressed surrounding the interview. I.e. if you plan to wear one level of dressiness the whole time, you need many fewer clothes.
- 100% wool suits. It's worth the quality over blends, and much more wrinkle resistant.
- Think about in-ear noise canceling headphones (and/or earbuds). They don't work quite as well as the bigger over the ear noise canceling headphones, but the space savings is large.
- Figure out how to pack all your toiletries in something refillable that fits in the quart baggy. 1oz of shampoo lasts longer than you think.
- Be prepared. Carry a small selection of over the counter meds - that antacid or acetaminophen when you need it, definitely comes in handy. I have very small case with about 2 each of a 4 or 5 different megs, and a couple of bandages. I end up using something on about half of my trips. A power bar lives in my bag.