There's a very important point for me to clarify. When I talk about political interference, I'm talking about it once the government says to do something. In other words, under the agreement on internal trade, we now have very significant legal consequences if the process is undermined in any way. What happens before the government says go is a whole different story. In my mind, that's not political interference. For better or worse, that is government doing its job. So everything you've talked about in those examples is not political interference in the process to buy something, but the overall scrutiny that occurs before the decision is made—sometimes being done better and sometimes being done worse.
You're quite right: it's up to the government, through its policy paper, to make the decisions on what kinds of capabilities it needs. Are these the four they think are up on its list? Different governments may have different points of view, and that may change from government to government.
Having said that, this is why having a defence capability plan, approved by cabinet and having gone through scrutiny here, would be invaluable, because it takes it away from that. With integrity and objectivity, people can ensure the linkage between a capability plan and a policy statement, irrespective of the government that comes into play.