This is a matter of both the RAW, the RAI, and the flavor text being at odds with the crunch.
It was already identified as a problem in another thread that the Green Hag cannot disguise herself as a beauteous humanoid maiden because she's a monstrous humanoid and Disguise Self now has this new addition in Pathfinder:
You cannot change your creature type (although you can appear as another subtype).
What this means is that not only can Green Hags not do something they're supposed to do, but the spell is considerably less useful than the plain Disguise ability, which doesn't specifically say you can't disguise yourself as another creature type.
Consider, for example, a human female with a Disguise kit. With some green face paint and a green wig, she can disguise herself as a green hag, which is a monstrous humanoid. With a few bits of ivy and/or daisies stuck in her hair and maybe some acorn earrings, she can make the same make-up into a dryad costume, a fey. If she goes for the whiteface, red lipstick and some fake canines, she can go as a vampire, an undead. Or she could keep the green make-up, roll in the dirt, and accessorize this a grisly hambone and go as a ghoul, another undead.
Disguise Self can't do this, unless some interpretation lets you go as a human costumed as a hag, a dryad, or a vampire or ghoul.
Any fix for this, apart from redlining the new line? Any idea why it was added in?
What this means is that not only can Green Hags not do something they're supposed to do, but the spell is considerably less useful than the plain Disguise ability, which doesn't specifically say you can't disguise yourself as another creature type.
Consider, for example, a human female with a Disguise kit. With some green face paint and a green wig, she can disguise herself as a green hag, which is a monstrous humanoid. With a few bits of ivy and/or daisies stuck in her hair and maybe some acorn earrings, she can make the same make-up into a dryad costume, a fey. If she goes for the whiteface, red lipstick and some fake canines, she can go as a vampire, an undead. Or she could keep the green make-up, roll in the dirt, and accessorize this a grisly hambone and go as a ghoul, another undead.
Disguise Self can't do this, unless some interpretation lets you go as a human costumed as a hag, a dryad, or a vampire or ghoul.
Any fix for this, apart from redlining the new line? Any idea why it was added in?
You can do one of three things:
1 - change disguise self so that it can only change your appearance to conform with a humanoid creature (regardless of type). This should be a general change to the spell in the game.2 - change the green hag. Let her be an exception to the general rule so that she can change to humanoid.
3 - do nothing. The Bestiary states that the green hag is fond of "assume[ing] the form of alluring young maidens". It states nothing of race, type, subtype or otherwise. In theory a monstrous humanoid can look alluring and young too.the only real restriction is that the new guise of the hag must be humanoid. You can rule that the hag looks human-like though not quite human.
Even within the rules I cannot see why the green hag should not be able to use disguise self to look like an "alluring young maiden". I would go with option 3.
I think the line about changing your creature type is simply meant to indicate that you don't change drastically enough to gain anything save a +10 bonus to Disguise. So, in all your examples, you're still a human, you just *look* like an undead/fey/monster.
I think this is the only sane way to go with it, especially since most times you can't tell some abstruse thing like "creature type" without a divination spell.
I think the spirit of the spell is that it's an illusion that lets you appear as any creature you could appear as with some good costuming provided by illusion. If you're a human, disguising yourself as a hag or a medusa should be easy, since they all shop at the same tailors. Disguising yourself as a centaur, OTOH, is probably beyond the spell, but it should allow a centaur to disguise themselves as a lion-bodied lamia, or alternately, a regular human riding a regular horse. (One imagines a horse-head codpieces and a pair of fake legs are a common costume piece among citified centaurs.)
I'd say stick with the original spell from the D&D PHB. Simple enough.
I mix and match 3.5e D&D with Pathfinder RPG. Some of Pathfinder's stuff I do not like (like the revised Bard's spell list and the fact they took Song of Freedom off their bardic music list).