I know it's never coming back, but it was so unique imo. Didn't require any gear grind because SO's were always enough to pvp on an even playing field. The pvp took skill and a lot of builds were viable. Then IO's came in took all of that away. RIP CoH pvp.
Honestly the big change to PVP, making all the powers work in a completely different manner in the PVP zones, was a big factor in driving me away from the game. I'm not much of a PVPer but to make it so if I set foot into a PVP zone to run a mission I'm playing a different game where a PVP build is basically required ticked me off no end.
PVP builds were basically required anyway, you just didn't know it. I still remember someone saying that if they wanted to PVP they'd bring their A-build and not an AR/Ice blaster, and Castle's response was very measured and professional, but I got the feeling he wanted to shake that poster and tell them the fact that AR/Ice blasters are automatically crap no matter what else they do is a huge problem that I13 was intended to fix.
But I also think that part of the problem is that they tried making PVP attractive to people who don't PVP, and...well, just speaking for myself, the reason I didn't PVP was the PVPers. The two major PVP guys on my server were such unbearable jackasses that knowing that having fun would require me to interact with them and their mouth-breathing ilk drove me away from PVP more surely than any mechanics ever could have done.
And before anybody starts, yes, I know that there are cool PVPers out there, who are willing to talk to you like you're a fellow human being and help you with any build or gameplay troubles you're having, but they were vastly drowned out by the jackasses like Budweiser.