Ok, a tank.....

3 stances instead of the normal two, MT, OT, Support.

MT - Boosted arggo, boosted defense but at 15% instead of the normal 20% because it adds a "Damage MP" effect which makes damage effect the mana before eating into the HP. The constant mana eating will add to the difficulty of holding hate making it balance. Alternatively keep it like the other MT poses and just give a damage mp skill.

OT - Normal stuff.

Support - For this to work I assume RDM would have a good PLD-like healing move as well as other Bard/Machinist like support skills. This stance would boost the effectiveness of healing and support skills on the RDM and party members.

Skills - main stats being VIT and INT for damage.

Fire Missile - Shield Lob, Tomahawk, exc
Frost Bite - Stunner
Electrocute - AoE Arggo
Healing Light - Self/party heal
exc

Tanks need heavy armor so do that, we can glamour and tanks have access to robes too so glamour is no big deal, just make the af gear sexy.

Rapiers/Sabers I think would be best. Single or duel-wield, either are good. I bet Ilberd turns out to be a RDM, and its a job from Ala Mhigo... (blood mage).