My apologies. I think I misunderstand what you mean by "ecosystem". All of your requirements are fulfilled by the tools I suggested. The guides I provided show complex typesetting (mathematics and otherwise), eqn does complex math expressions (more powerful than TeX according to Lorinda Cherry, the neateqn implementation by Ali Rudi allows for using TeX bracket syntax as well), pic and grap provide complex (2D) graphics, refer and bib2ref/ref2bib provide bibliography management, and all of it installed from a single repository and makefile (maybe this is different than an installer framework?) to under 43MB (including demos and acm fonts). XeTeX/XeLaTeX seem to only add support for utf8 (as I mentioned, natively supported by the plan9 *roffs) and various font formats (at least supported by neatroff, I haven't checked the others). Of course, pretty PDFs was the original point you quoted in the parent.
You should at least check out the neateqn guide for examples of math typesetting (even output in Computer Modern). But the original guide, as well as the others will show many more and different examples. These aren't groff guides. You might be surprised.
You should at least check out the neateqn guide for examples of math typesetting (even output in Computer Modern). But the original guide, as well as the others will show many more and different examples. These aren't groff guides. You might be surprised.