This RFC proposes a modified version of T105652: RfC: Content model storage, where a new table for storing content meta-data is added instead of adding columns to the existing page, revision, and archive tables. This would be a first step towards allowing multiple content objects (slots, streams) per revision, as per T107595: [RFC] Multi-Content Revisions. This was originally submitted as a belated comment to T105652. Filing it as a separate RFC was done to allow it to be discussed as an alternative T105652, though it is really just a modification of the original RFC by @Legoktm.
Three variants are proposed for the new table: a basic one which only includes the columns in the new content table that are needed to represent content model and format, a medium variant that also introduces a field for the content "role" (slot or stream name), as needed for multi-content-revision support, and an extended version that introduces all fields needed for multi-content-revisions, like length and hash, right away.
Rationale: While the needs that drive T105652 and T107595 are quite different, their solutions overlap significantly, namely changing the way content meta-data is stored in the page, revision, and archive tables. The idea behind the this RFC is to kill two birds with one stone: allow for more compact storage of content model and format as well as add an indirection between content object and revision. If T105652 and T107595 were implemented independently, their implementations would interfere or may even contradict each other.
The driving consideration for this proposal is that schema changes are disruptive - not only do they need work by database engineers and updates the MediaWiki core's code, they also mean a breaking change for extensions, tools running on Cloud-Services, as well as for any consumers of the raw SQL dumps we provide for download.
Update 2016-09-05: The details of this RFC are now maintained as part of the MCR proposal MCR Content Meta-Data Database Schema.