Nitpicking as it's not your core point, but I don't think you could do this with an Environmental trigger - according to the core book, the item is only subject to major magical changes in the environment (such as sunrise/sunset, or changes in aura), so you'd probably have to do it via a linked trigger to an InIg effect.
I do agree with the core point that it's the core effect that sets the level for MuVi purposes, not the effect modifications.