It felt incredibly forced in the movies and tv series, and i feel it would only feel even more in a p&p game.
Basically, everyone with a brain goes 'hey, why are we doing this shit' and 'power of course' (for the bad guys) and 'we need to defend ourselves' (for the good guys) is the answer, but then 'but why do i obey these silly rules, like 'no 2 on one' or 'only swords' and 'not on holy ground maaaan' and the answer usually is 'uh. Some guy tried it 2400 years ago and it ended badly', like idiot utilitarian atheist youngsters looking for power actually believe elders (although, even worse, only the holy ground restriction is explained like that).
Not really.
I mean, in the movies there are only like four immortals left. In the first it was Fasil, Kastagir, MacLeod, and the Kurgan. And all of them were effectively immune to bullets due to a much higher regeneration rate than in the series. If it isn't a decapitation, it's not going to slow them down much. The other two movies don't exist, but if they did, they would have similarly small and ancient casts.
In the tv series, plenty of immortals took shortcuts. Kalas hit a guy with a car. Xavier St. Could worked with a mortal hit squad. The Four Horsemen worked together until they they broke up. There was that one guy who thought he was God, and put together a team of immortals to fight his enemies. And plenty of young immortals think it's a good idea to ambush an ancient one with modern weapons or trickery. Most die in the attempt.
The holy ground thing can be justified as an instinct more than anything. After all, they can somehow identify holy ground and know exactly where it stopps. I'd assume that's related to their ability to sense each other.
As for the Prize being power. That's the thing, no one actually knows what it is. They just know that it exists. I'd think that all of the power that's spread out between the immortals wants to get back together. That it draws them together, because it's totally improbable for immortals to randomly cross paths as often as they do, just on basis of population alone.
Anyway, Highlander doesn't work in an integrated World of Darkness. It has to be its own thing to work right, and the central themes don't mesh well with the WoD.
WHY?
Who would be stupid enough to let a Baali live, let alone let them on a team like that?!
That's like the Technocracy recruiting a "Suicide Squad" made of nothing but Formorians and Nephandi!
Hey, not everyone gets to choose who their sire is. I mean, really, it's the LA riots right. Everybody is smashing shit and stealing TVs. And, you know, you could actually use a TV. So you go out with some friends, and you find an electronics store whose window has already been smashed, quite helpfully. And someone is already in there, but you know, there's more than enough TVs for everyone, not like he could carry them all out himself, so you don't think that'll be a problem. But then you notice that the store owner is there, and the other guy is, in fact, eating him. That's the point when you know that you need to get out of there, but as soon as you turn around something hit you. Next thing you know you wake up naked in the middle of a giant pentagram made of blood. And it's only after careful investigation that you learn 1) you're a vampire, 2) you've been possessed by a demon for the past week, and 3) you can shoot fireballs from your hands. Now all of your homies are dead, you're wanted to the police, and all the other vampires think you're evil for some reason. I mean, hey, Pot, the Kettle is on the phone.