Instead of having personal chunks, you could have chunk loaders that people could buy for 5 dollars to have 1 chunk loaded 24/7. You could reduce lag by slowing down machines that is not in the chunk that the player is in.
Offline chunk loading would be terrible in some packs. Some packs also have built in chunk loaders, than when paired with an offline loader, could allow someone to load their entire base while offline. Aside from that I've seen people build entire bases in a single chunk, it's crazy.