Would anyone like the concept of starter Pokémon having alternate final forms?

I'm not referring to regional forms, as was the case with PLA, but rather final forms that are influenced by other factors, such as evolving during the day or night (in the same way as Umbreon/Espeon).

For example, let's suppose that S/M had this mechanic. If you were to evolve your Brionne into Primarina, it would retain its normal form. If it evolved at night, its design would change to something more "evil," like an evil mermaid, one of those that lure sailors to the sea to devour them, and it could gain the Water/Poison or Water/Steel typing.