There doesn't need to be any legal framework in place that doesn't already exist. Contracts can take care of that. Tokens are just a way to keep track of investments and simplify the process of collecting funds. Furthermore, it's impossible to regulate ICOs. You can only regulate the change from crypto into fiat, which most people won't ever care about.
I agree with you in that blockchain technology in itself is impossible to regulate as it was purposely designed to make any government regulation unenforceable. That's a good thing. However, legal entities can be regulated very easily. So as soon as you have some company regulated and registered in certain legal jurisdiction associated with particular blockchain technology, that blockchain technology can be also regulated. For example, government can brought legal action against that company and force it to change its technology to be more complied with government regulations. So yeah, anonymous ICOs would be impossible to regulate, however there doesn't seem to be a lot of those right now.
EDIT: Another important thing. Although blockchain assets are impossible to seize, control or regulate, this is not true for any other real worlds assets. OP’s banana plantation can be shut down be government. Its property can be seized. So, when a blockchain asset is a representation of real world asset, it is susceptible to government regulation. In other words, making blockchain assets a representation of the property that exists outside of a blockchain itself voids the blockchain inherent resistance against regulatory interventions.
The worst thing a government can do is enforcing KYC for this type of venture. But even that would be a big upgrade from the current paradigm, which requires both KYC and very specific connections to even be able to invest in ventures. I'm assuming that both types will coexist in the future - coins with KYC and coins without KYC.
Depending on how regulation happens, companies might also just start their ICOs in specific countries that don't require strict KYC rules and thus attract more investors. In either case, governments and tax collectors are in for a ride... Very curious to see how this plays out in the coming decades.
I'm hoping that tax will just become voluntary and will be used in a transparent way that will make people more likely to pay taxes. If people knew that their money gets spent in good ways they probably wouldn't evade taxes in the way they do now. But most of the tax money gets wasted on bullshit, so it's no surprise that nobody wants to pay them.