Back when I was younger and rode tandem a lot, I learned to swing my leg over the handlebars. This avoided kicking my wife in the teeth swinging my leg over the back, which was recommended to be avoided.
If you're in the market for a new touring bike, you might look for a bike with a lowered top tube. Just one example: Velo Orange Polyvalient Low Kicker
Load carrying + ease of mounting/dismounting are some of the issues Dr. Alex Moulton addressed with his bikes, starting in 1962 and continuing through today.