You don't need data - because the point of Jake's letter/article isn't to create a complete recovery plan for the Irish economy, but to put default on the table as a realistic option.

It's a political move, not a practical one. The aim is to persuade the public and the incoming government that default is worth considering, and that it's potentially a better choice than the current ECB/IMF suicide note.

There's no need to deal with specifics until there's a consensus that default is worth considering in the abstract.