The 0.000159% is an unfortunate rounding error and is definitely unintended.
Yeah, I realised, was just joking. Having said that, if it was being implemented, it wouldn't surprise me if someone objected. You would no longer be able to say that the max number of Bitcoins is less than
27* million.
Handling things as a soft fork has interest incentives. It benefits those who hold coins already, but means that miners would be accepting lower payouts. If miners are mainly mining and selling their Bitcoins, then they have little incentive to agree. Many miners probably have some bitcoins saved, so it might work.
As you said, miners can always accept a smaller fee, but (as you said as one alternative) I don't think the incentive to take a smaller fee now to potentially slightly increase the value of their hypothetical holdings sooner is there.