I've taken the liberty of moving most of the math guts out of MediaWiki core
into its own Math extension:
We meant to do this years ago -- I even got partway through it once but got
held up on the horrid Special:Preferences system we had back in the day and
never finished it. The modern Preferences class is a lot more flexible, and
I was able to just grab the function that sets up that portion of the form
and move it over. Yay!
There are a few cleanup bits still to do; I didn't want to dive into the
message files just yet. There are some legacy interfaces on Language for
getting the math option names, so that'll need a little more fixin' to
remove those (the strings _should_ all be in the regular message area now)
and then break the message files out.
People doing third-party packages of MediaWiki should take note: the texvc
subprogram source will live in the extension now, not core, so build scripts
for 'mediawiki-math' packages will need to be updated.