Thinking about Kagamine NT.
My ideal Kagamine update pack would be like this:
Rin "Act3", Power, Sweet, Warm, "Dark"
Len "Act3", Power, Serious, Cold, "Light"
Rin Dark would be a serious-toned voice for Rin like Miku's Dark, with a bit of a Neru (fanloid) tone. Len Light would be a cute-toned voice like Miku Sweet that's like a boyish Lenka.
This would allow a producer to smoothly transition between the two characters in a song without too much contrast.
Just imagine, Rin Power > Rin Act 3 > Rin Sweet > Rin Warm > Rin Dark > Len Cold > Len Serious > Len Act 3 > Len Power > Len Light > Rin Power and repeat.
The Act3 voices (could just be called Native or Original+) would be their original tone from Act1 without that Power tone, but updated to the standards of Append. Yes I know Power is pretty much Act3 but aaaaaaaghhhhh.
This ideal pack makes no sense but I just really like the idea of them being a gradient to eachother, even if they kind of already are.