|Alexander MacLeod RPG Superstar 2008 Top 16, 2010 Top 4|
|Ross Byers RPG Superstar 2008 Top 32|
When new mosters, such as the ones you specify from the Pathfinder AP Bestiary, are introduced, it is up to the author of the new monster to explain how that monster might be created by Create Undead, if it is even possible.
It should not be changed to a 'create all undead by some metric' system, for two reasons.
1) Some undead, for story reasons, can't be created by mortals. Like Vampires and Ghosts. Others, like Liches, are created by Mortals, but not by these spells.
2) Some undead have unique powers which would boost their 'effective character level' when on the party's side, but not their CR when opposing them. This is similar to why a Grig with a fiddle is on Summon Nature's Ally IX. Despire being very weak, he provides access to Irresistable Dance, a high-level spell. Similarly, a human commoner ghost (see Alastor Land from the first Age of Worms adventure), has a very low CR, but some VERY potent spell-like abilities, like Telekinesis at 20th caster level.