You are right about the Touch ID not working if you replace the home button. You'll be able to use it as a home button but it won't read your fingerprints anymore.
What you say about someone re-soldering it is true as well. Anything that can be done once (1st time was in the factory) can be done again. It does depend on where the Touch ID snapped off though. You'll have to find someone who is good enough at micro soldering to do this, and most of your local repair shops won't solder let alone do advanced soldering like that. Check and see If any of the flex cables are ripped though. If they are you're basically out of luck and will need a new home button.
I know this isn't the best new but I hoped it helped. Good luck!