Creating the image itself should be very low overhead.

A while ago, Colin reorganized the spin kickstart files so that we have
a fedora-live-desktop.ks file from which the livecd is generated by
merely subtracting things that would make it too large (see
fedora-livecd-desktop.ks). So, ideally, using fedora-live-desktop.ks
should produce the larger image that you want.

But just producing yet another spin variant doesn't solve the problem,
really.