I believe you're looking for ISO 28500:2009, aka WARC, the Web ARChive file format.
-- ISO 28500:2009, final draft
The development version of wget can output to WARC.
The Internet Archive has many of their tools published on Github:
warc-tools is a Python-based suite of tools for working with WARC files, though not technically a "viewer".
Archive Team has a writeup of wget with WARC output, including links to the final draft of ISO 28500:2009 and implementation guidelines from the WARC usage task force.
The United States Library of Congress has some analysis of the WARC format with respect to its suitability as a sustainable digital format.
The problem is that most of the 'solutions' are browser specific, and they're not really intended for archiving:
MHTML likely has the widest support for reading, but if I were to do it, I'd personally be inclined to grab the whole site (rather than a single page) and re-write it using similar logic as
... and for reference, the Internet Archive uses a file format they call ARC (more legible alternative, if you bump the font size up), based on 100MB groups of files. The Web Curator Tool also uses ARC.