First initial thought bubble:
Out of the blue thought, would be cool if certain sets had transforming qualities, like you can only get this set through a rigorous solo arena built for tanks, your dps doesn't matter too much, as the mechanics and the hits from trash and bosses would instant kill a squishy DPS, DPs can't think like oh I can breeze through these low HP mobs as the environment causes a heavy slow affect (80% slow) if you're not wearing heavy gear, resistance goes up for mobs and bosses for every 300 weapon dmg past say 2500, a dungeon for tanks, and by the end you get special frost, flame, or earthen gear that will transform you into a mini atronach of that elemental, that gives special tank skills based around that element.
Second thought building on idea:
Like not a full atronach, but your character turns into a humanoid version of it, weapons and gear transforms with animated flare to the weapons based on the elemental gear you're wearing. You can mix/match gear for the stats, but won't get the transformation, each gear has different base stats and of course different elemental skills like the werewolf transformation all geared toward tanking, like the base weapon skills change...puncture on a flame transform would cause weakness to flame damage on top of the major and minor breach, your block has a higher resistance to flame damage, destructive clench with your transformed inferno staff adds taunt to the knock back of the fire staff passive.
Third expansion of the thought for all Roles:
Or better yet, there is only vet mode, but you chose the role you're playing upon entry and the dungeon loads according to role, so gear drops are role orientated, transformations look different for what role you are and skills change to appease DPS, Healer, or Tank. Base skills for weapon change with transformation depending on element, frost staff on a frost transformation for a tank adds major brittle on destructive clench.
I never gave this idea thought before, was talking to a friend an hour ago, about wanting a motif that really emphasized frost with animation effects that "Frost Caster" comes short on. Then the thought of transforming came to mind and I just build on the idea.
This would be a massive undertaking, but could re-define roles, of course this can be tweaked, changed, and made more realistic as it's only a momentary thought.