I think this is will be more trouble than it is worth for most people, but I'll outline some steps. Note I did not try this myself so there could be unforeseen complications (but I'm fairly certain it should work, if done properly). I have not gone into detail about accessing
.rpm contents, building a kernel/initramfs, configuring grub, or creating a DVD (you'll need to produce a new copy) as these are all things better dealt with in individual questions (most of which probably already exist).
Rpmfind lists the most recent kernel .rpms here, but those do not include an initramfs, which you would need to make them boot. They do include a
/lib/modules directory from which you could assemble one. A better idea might be to build a kernel for your system (using whatever distro) that does not require an initramfs, and use that.
The kernel used by the install disk is
/isolinux/vmlinuz0. You can replace that or add an alternate grub entry in
/EFI/BOOT/grub.cfg; if you are not using an initramfs, you don't want the entry to reference such, obviously.
If you go the custom kernel route, you may be able to get away without a
/lib/modules/x.x.x although this could take some trial and error. The root filesystem is in
/LiveOS/sqaushfs.img. You can mount that, e.g.
mount -t squashfs squashfs.img /mnt/squash. Inside that there's only one file,
/LiveOS/ext3fs.img, so after you mount
squashfs.img you can
mount -o loop /mnt/squash/LiveOS/ext3fs.img /mnt/img. There's a
/lib/modules directory in there into which the stuff from the kernel rpm should go.
Of course, the image you've mounted from the DVD is read-only, so to create a new one you'd have to copy that, make your changes, then write it out to a new DVD.