Given Tokimeki Tonight has both a Magical Girl and yakuza in it (albeit not a magical girl yakuza), naturally it's right up your alley
Speaking of Vampire Magical Girls, I've been formulating ideas for a Vampire Pretty Cure fan-season (starring a sire-sired duo), which has got me looking into how the ideas of 'vampires need to be invited in' and 'vampires obsessing over counting' came to be.
At first I thought vampires needing to be invited came from their aristocratic image and etiquette, but I found out that needing to be invited goes back to the 17th century, before they were thought of as aristocrats. My other guess was that it's due to the idea of thresholds being sacred and mystical you see a lot in folklore, and from what I found this seems to be the case
I couldn't find much for why vampires are linked with arithmomania (the name for counting obsession) beyond speculations. My own guess is it has to do with folkloric beliefs in numerology of numbers having an inherent power, but I've also heard it may be to keep track of time since vampires would have a different perception of it, being undead and immortal and all