Simple solution to everyone worried about cheaters.
Make it so offline characters cannot enter the online mode. D2R?
Yes D3 became a horrible cheating ground even on console but here is another funny thing, you can make the choice not to play with people that are cheating and can make the choice not to use the duped uber gear they drop which is not an issue here anyway since all loot is per-player and most gear cannot be traded anyway. Also reporting players would obviously be easier and have harsher consequences here. So I see no issues.
There are going to be cheaters no matter what you do, there is no game that people just don’t even try to cheat.