Set another account up allie urself to it and stick a big guntower in ur base with it stops them sneeky allies being in ur base without ur permission and you can always turn it off if you want them in ur base my friend done this verry effective lol
How about they make it so nothing bad ever happens, you can't be raided, tames can't be killed, never freeze or starve and have all the materials in infinite amounts with no weight limit.
That's the risk/reward behind having allies. Make sure you can trust the people you ally (if you do at all), and keep up tribe relations between them. An auto de-ally system would only have a place inside of dedicated servers (imo).
Had an alliance once in an official server, got on facebook one day and noticed them posting pics in here of our mutated ptera cave saying it was their tames, lol. I was like they really out here coming into our base when we’re offline