I got font rendering to work. As I predicted, it's simply a bug in Wine. If you call the Win32 API call 'GetGlyphOutline' with the format parameter containing 'GGO_UNHINTED', then Wine fails the call:
fixme:font:WineEngGetGlyphOutline Unsupported format 258
(258 = GGO_UNHINTED | GGO_NATIVE) Probably real Windows succeeds, but I didn't try that.
A good fix for that would be to gracefully fall-back to hinted fonts when you detect that situation.
A bad/hack fix is the patch I'm using instead: http://hg.et.redhat.com/misc/fedora-mingw--devel/?f=597377437067;file=inksca...
Anyway, with that, inkscape basically compiles and runs fine using our cross-compiler and Wine. I haven't found any other issues, even loading the large example SVG files that you supply.
If you want to keep track of our latest work, go to: http://hg.et.redhat.com/misc/fedora-mingw--devel/ then click 'manifest' then 'inkscape'.
Rich.