Thats something not hard to do.
Lock camelot up to tl6 limit.
Use another dungeon in 25% gas for tl7 pvp such as Will to fight, with a boss enconter like Tarasque as endgoal and lock it Tl7 instance only.
That would bring more people for both dungeons, in dif tl's
Something like this:
Camelot TL4-6 > Level 100-200 (with tara already level 200)
Will to Fight TL7 > Level 205 -300 beeing tara-like-mob level 300