I suggested something like this months ago and called it "Champion" It's better suited for the PLD. The difference is it's not a hate gaining tool but a hate passiveness effect. It reduces the hate of others in the enemy hate pool while maintaining the PLDS.
I like this but would also think changes to cover are needed. First reduce the recast of cover to about one minute and have it last one minute. Second make it an automatic cone effect behind the PLD for the enemy he/she is engaged with. While on the PLD automatically attempts to COVER any nearby party/alliance member attacked behind the PLD that he/she is fighting. To keep things in check It only covers attacks made by the enemies they are directly engaged with.
Cover attempts are made AOES are forced to be focused on the PLD when successfully covered, this makes the blunt of the AOE target the PLD. This cover will activate on both magical and physical attacks provided the PLD is directly engaged with the enemy attacking or casting. The success of a cover starts at 90% and reduces 10% for each successful covers till it hits a minimum of 20% or the duration ends. To keep hate in check with each cover hate is taken from the covered player as though they where attacked instead of the PLD.
Why not just give them a chance to auto counterbash (without stun) with a shield block or increase the duration and effect of the spell reprisal? Making PLDs DD isn't the solution. Changing them to them a better tanks is IMHO the best utility for the job. It's a TANK protector.
IMHO COVER is a super weak link on PLD the ability needs modified to make the job better as main or subjob. Change cover to protect ALL nearby allies behind them not just the one player behind them. Hate it or like it IMHO SE isn't going to make PLD a DD Job.
At least with cover changes like these they can truly be a TANK even with the bad enmity system. PLD shouldn't need the highest hate to tank effectively. This is a BIG issue that needs fixed for enemies that reset hate or DDs who can't go full out on damage. With changes to cover these DDs will still get hit just the PLD tank will be able to mitigate some of the attacks to them if they lose hate.
Some players may argue that this might make the PLD tank to well, I counter with WTF! If they're a tank and can't do massive amounts of damage like the DD's they're grouped with then they need something else to get a spot in an alliance. They must have something SPECIAL worth putting them in that slot over a DD. Since DAMAGE OUTPUT isn't a option they need to be equally useful in DEFENDING others who can provide better output if a PLD is used to mitigate damage. DD's should be allowed to Zerg but not 100% protected by the tank if they do. I Sincerely think fixing cover is the KEY to doing this.
I assure you make these changes and PLD will be a bad ass job that will make them worth while party spots in a lot more situations. Not just used for holding extra spawns.
Anyone that thinks that the cover changes I suggested are stupid please chime in I haven't seen anyone make anything even remotely better suited for making PLD a more viable tank without adding extra abilities or fudging with hate. In previous FF games cover was automatic and a trait/skill. I think having it as a trait would be broken because you wouldn't want it on in some cases. I also think it should have a duration that matches the recast and be easy to recast if dispelled.
Also a it'd be nice if they was able to use paralyna and poisona at level 25-30ish.