Have you looked at the WARC format? It's ridiculously simple, basically concatenated raw HTTP requests and responses, with some extra HTTP metadata headers mixed in (a la extra JSON metadata keys). You can open it with a text editor. Very simple and efficient to manipulate, and very efficient to iterate over or generate.

https://iipc.github.io/warc-specifications/specifications/wa...

Arguably the biggest problem is that it isn't complex enough: there is no index of contents built-in (the standard .csv-like index format of URL/timestamp/hash/offset is called CDX).

There aren't a ton of tools in the web archiving space in general, but almost all of the ones that do exist work with WARC. Existing tools (for interchange) include bulk indexing (for search, graph analysis, etc) and "replay" via web interface or browser-like application. Apart from specific centralized web archiving services that use WARC, there are several large public datasets, like Common Crawl, that are released in WARC format.