The problems related to blockchains are very well known. Blockchains have been used extensively at this point, for highly critical applications. They're the most censorship resistant platforms known to exist.
Care to name a point where a blockchain stood between MSS and Chinese dissidents? NSA and islamic radicalizers? SVR and someone Putin wants dead?
I'm stoked about blockchains as much as anyone else (heck, I quit a job at Google and spent a year playing with them when Bitcoin first came on the scene). But to say that they are a good thing to build on top of when facing adversaries that have 7 figure USD budgets and capabilities to perform active attacks on non-trivial chunks of the internet strikes me as just a bit naive.
Problems with relying on a blockchain to validate domains against sophisticated adversaries range from obvious to unknown. Not good.