Vocal I agree with, but there is a misconception on these forums that the people here constitute the majority of the player-base, rather than a tiny fraction of it. Even adding people on Global, you still have to factor in the large percentage of people who don't talk at all anywhere in game and just play by themselves.
I like this idea (though I think you have a typo in your last line in regards to both players being Player B).
The problem here is that there is (currently) no way to value a player's power without allowing some form exploit OR severely limiting the player's choice in which team they use, and not allowing them to change teams to adapt to opponents.
You could take an average of all the troops a player owns, but then you would see people not wanting to level up and trait troops to keep their over all average low.
You could take the Attack team's power level and use that, but either you have to stop the player from changing their team after the opponents are seen, or people will get the opponent list with a low power team and just change to a high power team afterwards (reverse 1 team defense exploit).
All this also ties into...
Part of the PVP score system takes into account the progression and guild of the player attacking, so unless players are in the same guild, with the same kingdom progression (stars and levels) AND are also the same hero level with the same mastery choices, they will always get different numbers. This is because fighting an opponent with a Team Power of 9000 and all kingdoms at 7 star will be harder for a level 1 player, than it will be for another player of a similar maxed out level as the opponent. You're rewarded for beating players that are stronger than you. And this is where things fall flat for the top end, there are no higher players, so they can't beat them.
This is also think is a good suggestion. But is something that wasn't really possible before Guild Wars, since till GW the PVP leader board was the only real competition between players (outside of guild trophy counts, which are a whole different kettle of fish), so limiting who could participate would have placed a barrier to entry that some people might have just not bothered with. (Despite how much they would end up playing if they did bother)
In summary, I think there are some good ideas here, but were not feasible till now (GW and the change to Unity). So I wouldn't be surprised if some of these ideas are ones the devs have already got planned for the future.