I don't know if there's a non-arbitrary line between 1.x and 2.x. I'm not going to argue against either position as long as it's reasonably clear which you use.
Well, you can surely make the case year 1 was v1. Let's go from there.
2015 - v1
2016 - PV takes over. You could say v2 starts, but many players from v1 remain. Style different.
2017 - few players from v1 remain. But 2 notable ones are DPs. The DPs play differently then from v1. And the team has gotten much younger. Is this the start of v2?
2018 - only one DP remains from v1. Maybe even fewer regular players. Completely different style integrated over 3 seasons of play. Has to be v2 at this point. If not v3 and v2 was the transitional period of 2016-2017.
And you know what? Who cares?