This is a suggestion, based on my opinion. I expect people to disagree or feel strongly about this suggestion, so I look forward to the discussion.
I love the look of these old zones and enjoyed them so much back on live just as much. It was surprised to see them tucked away in the back Ouro portal (or base porters) when I started playing on HC. Since they don't have contacts or system functions (tram to other zones, arena, AE, auction houses, etc.) they would be easy zones to switch with little time or resource investment. They could all be switched to Player versus Everything zones (including other players, like Warburg).
I'd say Echo: Galaxy City would be a great Level 1-15 zone. Echo: Faultline would work with Level 15-30 (imagine those huge drops off the sides of the tall cracks with a knockback!). Echo: Dark Astoria Level could be 30-49 ( imagine that awesome zone with the music and ambience!). I say cap at Level 49 to give a high level PvP zone without Incarnates.
PROS:
"New" Zones for PvP
Gives players another reason to visit the zone besides gathering the exploration and history badges.
CONS:
???
Let's hear it!