Vampire blood ingestion

[Firebarrage]

This seems like the kind of thing that sounds neat on paper, but terrible in practice.

This would make vampire feeding needlessly tedious and people will definitely poison themselves to ruin a vampire's meal (e.g : suicide during vampire feeding was disabled because people kept doing it to reduce blood value)

I don't think you would run into people managing to poison vampires that often. To do this you would have to either be poisoned constantly or manage to get yourself poisoned right before the vamp glares at you. In the first scenario you would just die to poison instead of a vampire, and in the second you would have to somehow know that the vampire was about to attack you, which is hard (and it would be much more effective to just get a weapon than to fight a vampire while poisoned).

And I'll say once again that it is ultra easy for a vampire to just scan someone to avoid all of this trouble if they want to.