electric shifting. Shimano Di2 system. You can put shift buttons anywhere.

I put Avid Speed Dial levers on some of my bikes. The ability to fine tune the brake cable pull ratio is pretty nice.

Not all brake cables are created equal. Some are thicker, some use stainless steel wires, etc. The longer cable run to the rear brake will have a bit more stretch. That can be a moderating factor for single lever control for 2 brakes. Like cars, the front brake should have a little more braking power. Canti lever brakes are easily ajdusted for cable pull so each brake can respond differently from the same lever. It's not that difficult to fine tune a single lever control for f/r brakes.