I think the 100% single player by design approach is actually really well thought out and intentioned, though there's still a part of me that will miss the chance to play with people I know. It would be really cool if our friends also playing es could have their characters appear in our game as Sims. Maybe with special or additional interactions.
To avoid needing to communicate online, maybe you could prompt the game to generate a code or a QR of your character that you can send to your friends offline for them to enter/scan in their own game. Still totally offline and requiring no reworking of the games infrastructure, but allowing you to load/refresh any of your friends sims into your game with you.