I've got some ideas.
Warrior with Staff that he would use as a spear. A Jump skill in the F2 slot could be cool, like the Dragoon class in final fantasy.
Guardian with Warhorn, virtue replaced by praying skills. Access to Well skills?
Revenant with Greatsword and a Samuraï based legend based on teleport and evasion.
Ranger with Rifle to be somewhat marksman.
Thief with off-hand Sword and maybe with a bit of support in it.
Elementalist with a mace and more based on dammage, since core, tempest and weaver seems to be more jack-of-all-trades or bruiser than that.
Mesmer with main hand Pistol could be interesting. Focused maybe on power dammage.
Necromancer with shortbow and deception skills could be interesting.
For Engineer, I have no idea and again, those ideas of mine are far from best, just brainstorming here.
Scepter thief as a boon support or healer + rework venom trait to use the thief's healing power.
Longbow, greatsword or hammer ele with a mechanic that focus on using one or two elements sounds fun. Or make it so 1-5 skills being arcane/earth/fire/water/air instead of giving us the 4 usual element swaps.
Off-hand sword (or spear if they ever make it a land weapon) power duelist/dps guardian would be nice.
Staff support/healer warrior.
Greatsword rev for wvw frontline/aoe damage.
I would love to see those.
the funniest post in the forum:https://en-forum.guildwars2.com/discussion/57204/please-stop-duelling-in-wvw
Engineer could get focus for a magiscientist elite spec.