We discussed in our most recent video the idea of migrating Blood Potency into OWbN. I've put together some thoughts on the matter.
Let People Ignore It
For a Blood Potency system to work in OWbN, it would need to be effectively ignorable by games that have no interest in running it. On a fundamental level this means that the two systems must somehow be made compatible.
At character creation, there is nothing that distinguishes these two from each other in regards to travel. As long as it costs at least 5xp in the Blood Potency system to get the effects of 8th gen, then everything here is fine. As the game progresses, things get more sticky.
In the Generation system, the only way that OWbN hasn't come down on people for moving down in generation is to Diablerize somebody. My expectation is that nobody really cares that diablerie happened, but the negatives be shown. This has a simple analog. In whichever system you choose to use to gain Blood Potency include amongst it the effects of losing a permanent Humanity and gaining black veins for a period of time. While one didn't commit the sin of eating another Kindred's soul, the taste of power does just as much to excite and bring power to one's Beast. On the surface, a character could be said to have done nothing wrong and even believe that, but the temptation to the Beast is no less real and ignoring its temperament is the pathway to Wassail.
Tell A Story
Make sure there's a reason behind and that people notice. For the sake of the system, it needs to be a reason that can't be stopped but can be suppressed. This will give us a literal implementation of the Domain Physics that so many games know and hate.
I haven't pinned down a story I particularly like, but something like the Gangrel Antediluvian has melded with the Earth and some cities aren't affected by the change to Blood Potency because of varying fault lines and how they affect her power. Steep this in some mystery, put a hex on it so the people with Knowing Stones can't just get it, and let's move on.