I wish that SE would add some personal LBs like how it's done in PvP. However, I'm tired of the whole "click button and win" LB. When you break a limiter, you need to have some drawbacks. For example, in Yugioh the spell "Limiter Removal" did just that, doubled all machine type's attacks but at the end of the turn they all die.
So for example, maybe in 8 person raids, personal LBs would be something like:
BLM:
A LB move called "Static Shock" that puts a 20s dot on the whole party that does damage. Thunder 1, 2, and 3 get proc icons (as in they are instant casts with full dot damage on hit), with recasts of 2s, 4s, and 6s respectively. Thunder 3 becomes aoe under the effect. So with LB active, you have to communicate with your party to do it at a time where heavy aoe damage is not happening. So more damage output from the BLM in that period of time, but at a tradeoff of party aoe damage. Also for that 20s, the BLM is rooted to his position, but can rotate.
SMN:
A LB that makes any aetherflow consuming move like fester/painflare cost nothing, and have no recast time. However, each time you use an aetherflow consuming move, the user takes 3k damage. So while the SMN can spam moves, they need to keep watch of the damage they are dealing to themselves so they don't kill themselves.
MNK:
A LB that opens all the gates, and gives 20s of Greased Lightning 5, doubles the potency of attacks, etc. However, after the 20s the MNK takes damage equal to 90% of their hp, and gets weakness + heavy debuff.
WAR:
A LB that holmgangs all enemies in a circular aoe around the warrior, followed up with a fell cleave on each enemy. Any allies including the warrior in the 10 yalm radius also takes the holmgang and fell cleave damage. Positional play would be important to not get allies caught in your "berserk".
WHM:
The LB consumes all mana, gives the WHM weakness, and takes away 90% of the WHM's current HP. It will restore the HP of all allies equal to the HP the WHM lost, along with give everyone protect and stoneskin buffs, and regen, and medica2 hots.
DRK:
A move that sacrifices 90% of their own HP, and as a result can either raise a target party member with no weakness, or transfer the HP lost to an ally to heal them, or do the equivalent HP loss as damage to an enemy. So the effect is dependant on what the DRK targets when the LB is used.
PLD:
A LB that can be used when the PLD is alive or dead. If the PLD is alive, it will transfer any defensive cooldowns the PLD has to a target, but make the PLD have the negative of any defensive cooldown transferred of the same duration (ie: target gets 20% mitigation from rampart, PLD gets increased 20% damage taken debuff). If the PLD is dead, it will raise the PLD, but give a debuff that cannot be removed after the raise. The debuff is that the PLD will instantly die if no defensive cooldown is up (like rampart, sentinel, etc.), so eventually the PLD will die and become double weak since he died twice.
That's just some random ideas I had for now, if you have a good idea I'd like to hear it too! The main point is that the abilities are "limit breaks" and are strong, but come with a downside. So the user either has to pick a good time to use it, or communicate with their group. Some abilties require the user to get their healers to pre-shield them because they will become weaker afterwards, some abilities are last ditch "oh shit" moves, and some are damage moves but make healing/dodging harder so they have to be timed right. I think overall the downsides are what makes the moves "fun", in that it would take some skill to use them to their full potential without killing yourself.