Remembering back to the glory days of wow, classic and TBC. Raid gear was on equal footing with the top tier pvp gear. This is what made the game extra fun for me. I was a hardcore raider, but also enjoyed pvp from time to time. Being able to just hop in and be on equal footing was grand.
The later expansions ruined this by adding pvp only gear, where if you spent hours and hours raiding, but wanted to pvp a bit, you would get face rolled.
I would be hopeful for gear to work both ways, not punishing a player out of one endgame because they chose the other.
I don't think that it's mandatory to have PvE and PvP gear in order to balance it.
We can achieve a balance with different talent builds. Swapping talents to get your PvP build is much easier, than grinding another set of gear.