These two arguments both imply stage 1 and stage 2 are both even more attractive than the chart shows. If you take the math seriously, stage 0 is pretty much never justified: you should launch at least straight into stage 1. The main argument that I hear against is: if a critical bug happens, it may be too hard to get 6 of 8 security council members to sign fast enough to fix it. But there is an easy way around this: give any single security council member the permission to delay withdrawals by 1 or 2 weeks, giving everyone else enough time to act.