I would make this the back story to a 200 year old home maintenance and repair bot programmed to repair and maintain a home and serve its occupants. Unless there is some back story included in the game, its story is open to the imagination.
In mine it wouldn't be a hero, The bot could provide a lot of insight into what happened locally. Abandoned with the family dog it could take care of the dog until the dog takes it's last breath. In it's lifetime the dog mates with other abandoned dogs and they stay around because the bot is programmed to sit the family pets. The pups grow up learning from how the older dogs of the pack respond to their bot 'pack leader' and other surviving domestic “bots in the neighborhood “, programmed to care for their family, the family pets and maintain their home.
The fallout wiki has such bots repairing each other to explain why the free roamers get along without humans able to maintain them. I imagine they can be tweaked and upgraded to do many tasks at higher levels; grounds keeper, gardener, accountant, tutors/companions for people with special needs, tireless, patient companions for the elderly, tutors for the children of ‘tiger parents’, a variety of medical skills from emergency medical tech, nurse, surgeon, veterinarian.
Abandoned the tweaked ones up grade each other and the other bots with parts and programs from the stocks of local cybernetics and computer shops, parts and program stores (imagine the high end custom programs and upgrades there might be for well to do ‘tiger families.’) Such bots could develop a lot of capabilities many owners might not have been able to afford. I prefer the original commercial/industrial/agricultural Handy bots of FO1 and FO2 to the home version of the later FOs. http://fallout.wikia.com/wiki/Mister_Handy_%28Fallout%29
The bot doesn’t have to be cutesy or witty, just a good reliable keeper of the dogs who react to them like they would people who care for them to the best of their human ability, (bots can be programmed to be attentive, consistent, patient and never cruel to their charges). Kind of like the T-800 in Terminator 2 with the young John Connor because that is how it has been programmed by the future John Connor.
Possibly show the bot or bots with puppies clamoring for attention and to be stroked, into middle age. Show the bot training and praising them and comforting them through out there lifespan because dogs like people like and need such attention. With proper AI I believe a bot could be a better very attentive keeper/companion, (learning to read and meet the needs of those they care for better than a lot of people.) Isn’t that what they would be programmed to do with the humans they serve?
The bots stray further afield to find needed resources to care for and repair their home and meet the needs of their charges, and are sometimes captured or looted and have to escape to return to their pack, though it might take years. Sometimes far from home, they find a new home, a new pack, in a settlement or survivalist community where they and their programming are appreciated.
Though few attack a bot, or bots from “the ‘hood” fitted with at least a blow or cutting torch, power saw, maybe edged weapons, maybe six arms, adding ax, meat cleaver, machete, hovering head and shoulder height with a pack of trained dogs in K-9 armor, fighting as family.
How do you feel about a bot who earns the love of an old dog it has comforted cared for all that dog’s life, and is there to comfort till the dog dies of old age with their faithful companion in attendance? There is a lot that talented artists could say about service and kindness, appreciation and love, selfless service, and “love not human” without being ham handed and wordy.