there's the rub---- something like konq dynamically linked against libs the Z already has, or, statically compiled but with a minium of baggage is what is wanted. maybe if we used the installed size of firefox as a 'standard'? that should leave quitre a lot of space for static libs n things, I would guess.
as to the space issue... even at 2x the size of FF, if it were speedy, powerful, had a smaller memory footprint, etc ..(and would work with eabi, maybe?) I think we'd be ahead of the game.
Edit: thought I'd do a little googling, and came up with
QLWM maybe building a light x11 / QT based wm and building konq into that would be worthwhile?
The site claimed the WM used about 16 megs, the project looked useable as is.... and appeared to be running konqueror