Firstly, I'm not trying to propose an alternative state-like institution that happens to be voluntary, but instead alternatives to the entire institution.

Secondly, I don't know what you mean by "the poverty that capitalism creates." When I say "capitalism" I mean "Capitalism is an economic system that is based on private ownership of the means of production and the creation of goods or services for profit." If you mean "capitalism" as in "the free-market that we have now" then I'm afraid we are talking about different things. It would appear to me that capitalism, as I mean it, has not really gotten a fair shake under the state (just as communism arguably has not) but it would appear that capitalism has created significantly more wealth even despite the state. In most cases where "capitalism" has created poverty, you can probably link the causality of that poverty to state actions.

The paradigm I am rejecting here is statism. I believe that using aggression to solve problems leads to more problems in number and complexity than the initial problems you started with.

Most people are happy with some kind of social safety net, in fact.

Well, I would suggest that the state doesn't provide this in any meaningful way. For any person they help, it comes at a much greater cost than it needs to to provide the same benefit. I'd be willing to entertain your construction of how the state is the only way to provide a "social safety-net."

Voluntary taxation is a bit of a conundrum. I mean, if you pay "taxes" voluntarily, there is already a word for that--it's charity. "Oh, but I love paying taxes. It satisfies my civic duty!" Well, see what happens when you all of a sudden decide you don't like paying taxes to fund a massive, deadly war abroad, paying into a shit-value Ponzi-scheme, and supporting the kind of class-warfare that only a drug war can prop up--let's then see how voluntary it is.