There are complaints that Tasker is a paid app. I bought it to handle this exact same work around. I then bought a Samsung phone so no longer needed the bt reconnect feature. However, if you seriously want your Gear Fit to work for you, Tasker can make it do almost anything.
I have my own security task that will lock the phone should it loose connection with my GF. I can also reboot my phone from the GF should it go wonky.
Well worth the money, if you're serious.