Drive side axle offset to allow wider freewheels isn't the sole consideration for axle durability (with common threaded axle diameters). It's also the difference of dive and non drive side loading. So if the non drive side had the same axle offset then both sides would share the loading equally. It is possible to design a bike around said axle/hub dimensions. But this isn't done almost all the time. Some will approach this by setting up their bike with a 140/145 rear hub spacing (as tandems have used for decades) to help reduce the axle loading differences. Before freehubs were the game serious touring bikes used this method. Andy.