The downside to that is that Miku is not part of this chapter at all. Especially writing this chapter, I realize that this story isn't really much of a Nanoha/Vocaloids crossover. It's a Nanoha story with some Vocaloid elements (mostly the character appearances) taken to appear as characters.
The most egregious example of that is the arrival of Kaito in this chapter. Or rather, a "Kaito" that bears no resemblance to the Kaito of the Vocaloids, acting only as a weapon to be used by Doctor Haynes. He's not a Vocaloid, even if he does have the element (the Musical Ritual System) that defines the Vocaloids in this universe. Perhaps that will change someday, if I ever write a sequel to this story, but for the moment Midchildan Music is and will remain primarily a Nanoha story.
This chapter also introduces the two main antagonists of the story. We've had glimpses at Doctor Haynes before, through his conversations with Chrono and Fate. I went to no effort then to try to add a whole lot of nuance to his character, and honestly there's not a whole lot there now. His only goal is to advance his research, in the truest vein of evil mad scientists everywhere. I'd like to think my description of his physical side breaks the mold a little, but that's not much of a nuance.
Michael, on the other hand, is still a villain despite a reasonable amount of favorable characterization. He is open and honest with the Sergeant, assuming (wrongly) that he will be working together with him in the future. And acting on that assumption throughout, he helps the Sergeant to upgrade Miku, and inadvertently gives him a tool that will become very useful in the next chapter. All the same, Michael has no concept of Miku as anything other than an object. He sees nothing wrong in programming Miku to want to sing, knowing that the Miku he wants to create will never be able just to sing without activating a new magical weapon.
And speaking of new weapons: the Musical Ritual System, the MRS of previous chapters. I will happily join the tradition of creating a new weapon and setting a story around it. The Belkan style from A's, the combat cyborgs and AMF of StrikerS, and now the Eclipse Virus from Force... every new season of Nanoha invents a new and ever more deadly type of weapon, magical or otherwise, and challenges the protagonists to deal with it.
The MRS began as an excuse to factor the Vocaloids' songs into the story, but at this point I would call it a new addition to the Midchildan style. The Nanoha-verse seems to lack what I would call true ritual magic, spells with complicated and lengthy preparations that can only be directed in one fashion. The series has a definite focus on functional magic, so this comes as little surprise. And the Sergeant can try to add in functional upgrades all he likes; Miku's magic will never be as fast or as variable as Nanoha's or Fate's. Whether he can use it in combat all the same... well, that's a question for the next chapter.