I've heard that electronic shifting is just a whole other level of performance that even a perfectly adjusted cable system can't approach. It deserves the rest of the bicycle to be high end also. Sounds like the OP is looking for "serviceable" as most other folks here are also. I have not heard about anyone thinking about touring on tubulars either. So for this application there are other ways to do brifters and low 20's gearing rather than Di2. Mine is Sram, 2x10, 28-42 chainrings
Lots of options if upper 20's is good enough.