Been thinking about this a lot with the current GW1 anniversary, as well as doing map completion as I work my way through Path of Fire and LW Season 4.
Guardian was made as a mix of monk and paragon, revenant pulls a bit from Ritualist, Thief was really a rework of Assassin.
I think Dervish could stand to come back as a 10th profession. I've seen arguments that it should be an elite spec, but there's enough from it that it could stand to be it's own class.
Scythe could be introduced as a new weapon, their specializations could revolve around the traits from the original (wind prayers, earth prayers, scythe attacks, mysticism)
They could pull from elementalist attunements and have a god path to follow that affects their attacks