That's it. You will need ext2 support (for example provided with the excellent multiboot) because the lib directory is full of links, FAT is no good. But you don't need an ext2 formatted disk!

Grab this
http://rapidshare.com/files/74345596/qt.img.html
Check it's been correctly downloaded, you should have the same checksum.
md5sum qt.img
37ff9c4f6744fcd48a952fb3d4f65aeb qt.img
Create a mount point and mount the image (as root).
mkdir /mnt/lo
mount qt.img /mnt/lo -o loop
Tell the system where qt libs are:
cd /mnt/lo/Trolltech/Qt-4.3.1/
. ./ld.sh
Try the bittorrent client included as an example:
examples/network/torrent/torrent
I've used the torrent client to download 100MB, works like a charm.

This includes a complete tree (usr/include, bin containing qmake & al, usr/lib ,..).
About ~70Megabytes.
External apps using qt<4.3.2 can be installed anywhere, simple be sure to run ld.sh before running it.
Proof of Concept that it can work with little effort.
++