If you want to defend the minimal state, you must argue in favor of its strengths. What are they?
An ideal sort of minimalism would incorporate a learning mechanism similar to market competition, allowing people to learn the characteristics of different ways of holding rule enforcers accountable. It would govern by consent. Defenders of democracy pretend that the status quo should satisfy us in these regards. Feedback and consent take the form of voting, volunteering, donating, lobbying, public opinion, etc. Caplan claims this more or less works as a feedback mechanism, that new unpopular policies will fail to pass, and old policies will lose support and face repeal as they lose popularity. For him, common cognitive biases take the blame for government flaws. All this depends on centralized mechanisms for collective choice, rather than decentralized and bottom up.
Sophists often frame our alternatives as an unpleasant dichotomy between the status quo and imagined chaos. This approach harvests at least a grain of truth, in that no one has created a serious test case yet. Innovators face a catch-22, in that people hesitate to embrace untested ideas. No one dares to test something new because it is untested.
Rothbard, Huemer, Rose, and more challenge the justification of the state's right to command and the people's obligation to obey. But Hayek points out that our lives depend on practices and beliefs that we cannot justify with rigorous philosophy. Philosophy does not provide only good ideas, or we'd all be Marxists. The problem with the status quo is that even if innovators and early adopters were willing to try something new, because of the collectivized aspects of politics, others will try to prevent their experiments and explorations. How can we overcome this obstacle?
Good arguments can take us only so far. We need well tested, well understood alternatives that people can choose for themselves directly.
Molyneux says we have tried minarchism and it failed. We tried several variants of it, and they all failed to some degree, but not all in the same way. Minarchism with consent, what would that look like?
Individual nullification: I can challenge, nullify, or contract around any law that applies to me. Only other individuals can be my counterparties, the state is arbitrator and enforcer only, not litigant. So crimes have a victim. (No malum prohibitum.)
Dynamic jurisdiction: Consent is insured by allowing the governed to vote with their feet and take their land with them.
Subsidiarity: Issues are handled at the lowest feasible level.
Strict Federalism: Different jurisdictions can do things differently.
Taxes: Can they survive? Will the voluntary minimal state be financed with an indiegogo campaign?
I can imagine a minimal state or competing defense agencies, but where is the strict line of separation? Minimal state supporters speak of monopoly, but the state is not strictly a monopoly even now, and it is hardly minimal. Minimalists should recognize this, as separation of powers and federalism are their big things.