Ok, been around checking the undead base monster classes.
-Didn't add anything to the ones that get scaling incororeability because even at first level it offers some nice utility.
-Angel of Decay gets Decay Device, that allows it to rot locks and traps and other objects.
-Brain in a Jar already had psionic stuff.
-Defacer gets to disguise as beings whose faces it has stolen.
-Drowned already has swim speed and curse water.
-Entropic Reaper gets an Intimidate bonus while wielding an oversized scythe.
-Ghoul and Wight get Primitive Predator, bonus to hide and move silently while unarmored and not wielding manufactured weapons.
-Nightwalker gets a scaling bonus to all skills whilein darkness.
-Pistol Wraith already gets guns, nuff said.
-Mummy gets bonded servants, aka unseen servants with some tweaks.
-Ulgurstasta has the acid breath at first level, if you don't know how to use it that for utility then I can't help you.
-Vasuthant has unbounded flight right away, and is medium sized and Str-focused, so you can carry the party members across most 1st level terrain obstacles, scout the skies and whatnot.
-Vasuthant gets to disguise as its victims.
-Bloodhulk gets a bonus to Intimidate while bulging up.
I doubt the immunities being a defining point of being undead is a just argument since many abilities that define certain creatures in many monster classes are not available at first level. Them being part of the undead type doesn't justify it either otherwise the abominations would be getting all their stuff on their very first level instead of getting a little of it all progressively.
Get on with the days man.
Abominations haven't been a creature type for more than a decade now!
Specific creature abilities may be delayed, but basic creature type abilities are handed out at first level.