The top three reasons are perfect examples of worst possible assumptions, on which no sound engineering (especially of decentralized consensus-critical payment network) can be based.
Once again, BIP 101 is not the end-all be-all. It's a first stab at the problem, and a reasonable one at that, imo.
But let's take the worst case scenario: technology ceases to improve whatsoever, transaction volume skyrockets enough to fill all blocks 100%, and all the miners (irrationally) choose to jam every block completely full. In that world, a reasonable desktop PC running on a home connection, and with hard drives that today cost about $300 will have zero problems keeping up and storing the data, and operating as full nodes, until at least the year 2023. In that made-up, dystopian apocalyptic future, we would have to (gasp!) consider a fork... eight years from now.
Is it really reasonable to assume zero technology improvements in the next eight years? Of course not.