I'm trying to make a default replacement for the Maxis vampire dress that the grand vampires wear. I'm using the pumpkinhead dress from the Store. I've managed to get all the dress showing up correctly except for the alpha (the mesh alpha, not the other alpha).
I love to hear something can't be done after I've done it, it would be discouraging to hear it beforehand.
The thing with Default Replacement outfits (I assume that's what DR means) is you can override it at any point. The outfit you are looking at for example is given to Grand Vampire(ess) by GUID, you can override the whole outfit to be any that you like by overriding the 3DID Referencing that links that outfit, in this case that's Group 0x7F12F35A, Instance 0x00000003. Change the third line in that to be any outfit and that's what Grand Vampires will wear.
Alternatively that points to the Property Set in the Skins.package in Nightlife named afbodydressmedieval_red, group 0x2C17B74A, instance 0xAF8E6A35. To add more alpha components you'll need to extract that and the 3DID Referencing file of the same group and instance values. Add the alpha components into that property set and the textures to the 3DID Referencing file as well as change the mesh if you like the same as you would for any other outfit. (that particular outfit also uses a 3DID Referencing file in the globalcatbin.bundle.package, group 0x4F184AA9, instance 0xAFE81796 but you won't need that)
You could override just the mesh and/or just the textures in which case you will be limited to the same components as default. By overriding the property set and 3DID Referencing file you can use any mesh with as many components as you like.