To answer your question about installing GRUB2 by default using install scripts, GRUB2 is now maintained incore, and legacy GRUB has been moved to AUR. Therefore, by the next official iso release, GRUB2 should be a part of the official install, and the install scripts will be updated to support it.
As for tweaking /etc/rc.conf, you should be able to do this manually from within your install chroot before rebooting. Hope this helps. ~Kyle -- Kyle is a droid. The whole world knows it. This e-mail shows it.
