I know about flwriter because it used to be included in Damn Small Linux. It hasn't been developed in about four years and the last version was only available as part of XD640, a project for a desktop environment at 640x480 resolution for legacy systems. XD640 seems to have stopped at an early stage of development.
Edit: fltk-utf8 has been merged into the main fltk library so we wouldn't need an additional package for that. This is from the fltk-utf8 web page:
fltk-utf8 is not maintained anymore. It has been replaced by the official FLTK 1.3.x release.
When DSL dropped flwriter they went to Ted, an RTF editor, rather than a full word processor. I may get around to packaging Ted but I honestly don't think it's anything special.
You're right about AbiWord having bloated to the point of no longer being lightweight. When you take the AbiWord and Gnumeric deps into account they are approaching OpenOffice in size. They're not quite there yet but it is to the point that most people will probably just use OpenOffice, and that is what you are seeing on the netbook distros.
SIAG Office still wins out on small size and at least somewhat decent functionality, IMHO, at least for the spreadsheet and word processor. I'd love to see something else developed or at least see more active development and updating of SIAG Office.