There’s plenty of actual research into the ancient origin of vampires you can read without resorting to baseless speculation. There is no single myth or origin and eastern europe has no vampire bats—in fact, the bats are named after the myth. The connection is likely due to them simply being nocturnal.

EDIT: My tone came off as completely dismissing your thinking, which I don't mean to, I just mean to say that there's already a lot written on the topic.

Bat "bites" are only half the story. Bat scratches are really nasty. In ancient times they would look like bites and most always would become infected. Even today, in much of the world (ie usa) any contact with wild bat should be taken very seriously. The link between bats and disease is no myth.

Bats are also the common wild reservoir for lyssaviruses, like rabies. Bats are not highly susceptible to rabies, and can remain asymptomatic for long periods of time. If you wake up in a room with a bat in it, or if you find a bat in a room with a child, or otherwise disabled person, rabies post-exposure prophylaxis is called for, even if you don't find a scratch, or bite mark.