Ever since alpha, I always wanted to see a true sentinel class: shield only (and a massive one at that! 2-handed).
(Yes, it is possible to attack with a shield, but it would be the ultimate tank class wielding huge shields to protect the party members. Special moves to quickly cover the team, force harmful spells to hit your shield instead of a team mate, provides a backward cone of protection against AoE spells [anything behind you], absorb damages and convert them in HP, MP or TP... many options, but pushed to the extreme for the true sentinel class.)

It would be fun to be able to play as a true sentinel.
At least, it would help with tactics and allow more strategies against powerful foes.