I prefer Assume Supernatural Ability over Metamorphic Transfer because it doesn't have a daily limit and I'm only interested in one Su ability.
The problem with Assume Supernatural Ability is this:
WIS 13, ability to assume a new form magically,
Reasons that say NO
- Expanded Psionics Handbook goes to painful lengths in every single power description to separate magic and psionics. i.e. "nonpsionic and nonmagic"
- Reality Revision goes out of its way to say it can't reproduce spells.
- Psionic-Magic Transparency merely states how Psionics and Magic interact with each other. At no point does it say they're the same thing.
- All the counterarguments (see below) are implications from non-primary sources.
Reasons that say YES
- Magic Item Compendium
If you are using the Psionics Is Different variant (EPH 65), then an item created by a psionic character using a psionic item creation feat would be a psionic item. The guidelines given above should be used to determine the psionic item’s feat and power prerequisites.
This implies if you are not using the Psionics Is Different variant then items created by a psionic character using a psionic item creation feat would not be a psionic item. Therefore it would be a magical item. But once again, this is an implication from a non-primary source.
- Complete Psionic
In addition, you always treat magic and psionics as identical. Therefore, powers such as dispel psionics work for both magic and psionics. Most campaigns already treat them in this manner, so this mantle is most useful in campaigns where they are considered different systems.
The above is clearly saying under psionic-magic transparency magic and psionics are treated as identical. But again, an implication and a non-primary source.
So the question here is: does metamorphosis magically let you assume a new form?
I'd like to emphasize that I'm looking for RAW rulings/reasonings here.