After the Plunderstorm event, it gave some perspective on how progression and power levels work in PvP. I personally dont feel like the battle royal style of power growth worked well for WoW, however i do think the MOBA style would. Considering MOBAS were developed from Warcraft 3, and World of Warcraft is also essentially a Warcraft 3 mod, logically the progression system would fit.
Like in plunderstorm, entering lobby you can see other players around you and use the NPC to sign up for random battleground. You would have access to every talent point available and a base ilvl of 400.
Theres also a transmogifier there. Items earned in retail can be used to transmog equipment here.
Each match rewards experience to level which is gradually gained through time or by kills / objectives to a maximum of level 10.
The currency in each match is honor which can be used to purchase buffs for the match which take up a slot. These buffs can be merged into stronger buffs to enhance your character. A max of 6 buffs can be held at any one time. Buffs in your slots can be sold for a reduced amount.
You can preselect the buffs in the lobby before entering a match so that it prioritises purchasing that buff.
Buffs include things like primary stats, % on secondary stats, movement speed bonuses, cooldown bonuses etc
All characters enter the battleground with x honor. There could be an honor vendor in the BG spawn location which shifts to graveyard, or no vendor at all and can purchase buffs anywhere on the map with a shop UI. It just depends on how balancing works with certain maps like WSG or AB
Honor is rewarded with time with experience. A maximum of 10 levels can be gained in the match which adds to base stats. Once match finishes, your level is reset back to 1 in the lobby.
Progression is horizontal with wins leading to higher ranks matching you in pools with players of similar level like Overwatch.