As already said, a charge line is the answer to your problem. I had to go that route with our Fusion, and it pretty much solved the battery drain problem.
Also, the Ford Fusion IS still flat towable, and always has been without any issues, if you get the hybrid version. Ford's hybrids have always been flat towable, and have a very solid reputation for such. We tow a 2013 Fusion hybrid, and it works great. IMO, its one of the most simple and easy FWD auto trans vehicles to flat tow. No disconnecting batteries or fuses, no crazy procedures to go through when hooking up, no stopping every few hours to crank up the car and run it to lube the tranny. Just hook it up, put it in neutral and go. The way it should be.
🙂
Will and Cheryl
2021 Newmar Baystar 3014 on F53 (7.3 V8) Chassis ("Brook")
2018 Jeep Wrangler JK ("Wilbur")