Well, building further packages from inside the chroot environment should be no different than building the base system packages. So yes, unless noted otherwise ( I guess for Qt), you shouldn't have a problem. Your post doesn't indicate as much, so I suggest you try out the BLFS
book to install other packages. As for building on a 64-bit OS, I haven't tried it so can't advise you there.
EDIT: I guess you can build 32-bit packages on a 64-bit platform. A multi-lib setup is required, though. You can refer to the CLFS
project for further information on setting up a multi-lib environment.