Not really a successor, but you may want to look at *roff (groff, troff, nroff). I don't know much about it but I remember its format being terse. It is the tool used for man pages. Since I have only ever heard of it in passing, I can't give you any more help with it.
For example:
.pl 10.0i
.po 0
.ll 7.2i
.lt 7.2i
.nr LL 7.2i
.nr LT 7.2i
.ds RF FORMFEED[Page %]
.ds LH Internet Draft
.\" --> Header/footers: Set short title, author(s), and dates:
.ds CH 2-nroff.template \"
.ds LF Postel, Braden \"
.ds RH October 25, 2006 \"
.ds CF Expires April 2007 \"
.hy 0
.ad l
.nf
.\" 5678901234567 check 72 column width 12345678901234567890123456789012
Internet Draft J. Postel
RFC Editor
Category: Informational USC ISI
Expires April 2007 October 25, 2006
.ce
Nroff Template for Internet Drafts and RFCs
.ce
.in 3 \" Basic indent for text is 3 spaces
.ti 0 \" "Temporary indent" for next line: 0 spaces
Status of this Memo
Distribution of this memo is unlimited.
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other groups
may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
