Remy will have a quest in the future. After all, wouldn't the courier wonder where this loyal, friendly dog came from? Someone had to have taught him to obey commands and respond to that whistle. Success leads to a player home.

I wanted the quest, and reward, to be something that made sense for the situation, and with an animal character, that limits possibilities a little. I will also leave a version up with no quest or player home.

---Future Mod Spoilers Ahead---

The quest will consist of finding Remy's diseased owner and 'burying' him (which is just going to be where instead of searching the body it asks if you want to bury him. Having a shovel in your inventory will be necessary, but there will be one nearby).
After burying the owner, Remy shows his appreciation by showing you his owner's farm and where the spare key is hidden.

There will be two available versions of the home, a lore-friendly, balanced home, and one with a hidden underground shelter which contains a bunch of awesome crap. Awesome crap meaning: Purify water, process objects into components like the Sink, remove radiation from food, autodoc with barber, a couple of cool, but not quite godmode weapons and armor. Maybe even a VR Sim.

Light Step explanation:
When you find Remy's owner, it will be all too obvious the man died because of a mine. Remy witnessed his owner's death, and thus learned to be wary of hidden traps.

Owner's grave:
Whatever you do, don't search it. It will only contain the owner's extremely damaged, completely worthless clothing. I have every intention of setting it so that digging up his owner's grave will turn Remy hostile, and seeing as Remy is marked essential, it means he'll probably kill you. Heck, maybe his anger at having his owner's grave disturbed will make him stronger....