Your comments

I'm not sure whether or not texcoord works on PSM since we don't have a license for that particular platform.

Rubén is right; vertexColor isn't accepted for PSVita either. I agree with you, Joachim - it really is a silly issue. I've started a discussion on the PSVita DevNet forums with the Unity devs about consolidating these naming conventions to be the same. My understanding is that the PSM and PSVita ports may have been handled by different teams, which would explain the discrepancies.

The PS4 changes shouldn't cause any conflicts, I don't think. In the PS4-friendly build of Unity, the HLSLSupport.cginc file it ships with contains definitions for mapping SV_Target/SV_Depth to the appropriate semantics. I'm not sure if those same changes are in the main branch of Unity. If not, maybe just add an option to the list of Target renderers, for those of us who are affected by it?