As the old regex joke goes, "now you have two problems".
idk, i think it would be cool to have a copy of every dns record on my hard drive
You can do that already now.
Kind of. You can get the nameservers (and glue records if available) for every domain under a TLD if the TLD makes their zone file available. See https://github.com/jschauma/tld-zoneinfo
Well kinda but that would be an incomplete snapshot. Versus a blockchain where every DNS record change is necessarily written into my copy.