B/c of a motorcycle-accident inflicted brachial plexus tear I ride with minimal use of my left arm and no real use of my left hand.
The accident was some time ago and I've come up with a number of adaptations.
I've used a brake cable coupler so that the right lever pulls both calipers. The rear derailleur works as normal (Campy Ergo) and I used a Kelly Take-Off to mount a friction shifter for the front derailleur.
My latest and I feel pretty successful modification is hydration. I use a Oasis One-Twelve system with bottles mounted behind my saddle.
Not my bike (no new pics yet) but pretty much the same setup as the bike on the left. There are other TT/triathlon systems that would do the job as well but this one holds a good amount of water (with 2 bottles) and is pretty straightforward and a bit cheaper than most of the others.
Wouldn't be hard to DIY but I couldn't find the valves that come out of the bottom of the bottles.
Hope this helps.