I have been doing this for many years, putting bulk DNS data in HOSTS and personal use zone files served from loopback addresses. It is easier than ever today with so many sources of bulk DNS data.
DOH now lets users retrieve DNS data from recursive DNS servers (caches) in bulk, using HTTP/1.1 pipelining. Here is a working example: https://news.ycombinator.com/item?id=23242389
Many years ago, I started doing non-recursive (no caches used) bulk DNS data retrieval for speed and also for resiliency in the event of outages. However the privacy gains are obvious. A rough analogy is downloading all of Wikipedia in bulk and browsing articles offline as opposed to making separate requests online for each article and generating all the requisite DNS and TCP/HTTP traffic. Openmoko's Wikireader experimented with the idea of offline Wikipedia.
Not only does the DOH provider get a record of all the user's DNS lookups, she can now associate each request with the particular user program/device that made it.