Honestly, this is some of the few small things that keeps me from going away from eR9/eRX. For comparison, Shimano's charging cable is bulkier and probably takes much more space in my saddle bag if I want to do the same strategy.
All the flexibility that comes with LTWOO are so user friendly, from the variable 10-12 speed, user replaceable battery, individual gear indexing, air vent for bleeding, great app for on-the-fly adjustments. I know Shimano/SRAM may already have most, if not all of these, but considering I can get eR9 for a fraction of the price (they are now even much cheaper compared to launch price and I got my second eR9 for $380 after tax), I am now a happy user. I am hoping the second and third generation of eR9/eRX would solve all the issues users are currently having. By then, I would not hesitate to recommend the groupset to others.
It's actually somewhat impressive that they managed to do all these in their first generation product, while avoiding all the patent minefield left by Shimano/SRAM.
where are you getting the er9 for $380?