To set the default elevator with grub2, just:
1- check current settings
# grep CMD /etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT=”nosplash”
GRUB_CMDLINE_LINUX=””

2- set GRUB_CMDLINE_LINUX=” elevator=noop ” # or whatever

3- run
# sudo update-grub

4- reboot and verify ;)