Well I used the gconf editor to change
/apps/osso/inputmethod/input_method_plugin
from 000_hildon_western_vkb to 000_hildon_western_fkb

..this made every click on an area with text input possible immediately bring up the finger keyboard. No more tiny stylus keyboard, ever! It only does this when the hardware keyboard is closed, which still isn't exactly what I wanted.

It seems like making a shortcut could be done with matchbox-remote, but I can't figure it out. Anyone?