My two cents:
Open Lockdown is a good direction, but it doesn't really do much to improve gameplay. I have seen more new faces in Lockdown games since the tier removal. However, I have very rarely seen a newbie continue to play after playing once. It's one thing to make PvP more accessible and another thing to make it more enjoyable for everyone.
In my experience, the main thing discouraging people from Lockdown is not lack of accessibility but the biased physics and the DPS-based metagame that has evolved around it. A new player will have a hard time enjoying games where the prevailing strategy is to shut people down before they can even make a single move. More often than not newbies are hunted down because they take no time to kill and give a free heart upon death.
A simple change such as doubling everyone's base health could go a long ways toward addressing this problem. Engagements will last longer and there will be more room for adaptability. A veteran player will have to waste more time if they want to hunt newbies, and newbies will have more opportunity to experiment with possible counter strategies.
on the idea of having a room where people can practice lockdown (and maybe even BN)
like a lobby where people can practice (I think people can imagine waiting rooms and game lobbies in other games where you can practice with bots or just practice your moves).
(But I don't agree with sleep>freeze in PvP, freeze can't be unfrozen by teammates while sleep can)
There needs to be more chances for people to practice the lockdown (or bn maybe) style that isn't introduced anywhere else throughout the game,
lockdown untied is a good chance for low-tiered players to participate but if they can't make strategies on their own before getting swept by the top-class players then they can't make the best of their games. It also makes it less fun for them (imo)