It probably doesn't fit exactly what you want, but I found Lout (http://savannah.nongnu.org/projects/lout) to be a suitable enough replacement for a lot of LaTeX-y tasks. I'm not a heavy LaTeX user so it's likely there's a whole lot missing, but I found the document structure and syntax to be a good deal simpler. In addition the installer is (iirc) only a few MB - I'm sure you can get tiny LaTeX\TeX installers or packages but the ones I've seen tend to be very "batteries included, plus a whole lot more" which is maybe a bit excessive.