You're talking about projection modifier, but that has little to do with Corona.
Nope, I'm talking about having a diffuse map with one type of UV in channel 1, and inthe same geometry, in channel 2 having the new UV layout made by the modeler, now think that you have all the character with all the textures ready, but all the UV layout has changed, you have two options, or you work again in the textures to adapt them to the new UV Layout or you project Channel 1 texture in Channel 2 UV Layout, and you have the new texture perfectly baked and ready to be used, and this applies for a variety of things you can do at the same time, like extracting different maps or whatever other thing.
You can do this with scanline (as long as scanline stays alive), but it's sampling technology it's not good at all, and if you have an specific material like the Corona material you won't be able to do it, so you have to convert all the materials, make the texture reprojection from Ch1 to Ch2 and reapply oyour materials again, so having this inside corona is good, you save a lot of time.
Cheers!