Sure.

Let's stick to tanks for the time being. You have a baseline rate of personal LB generation, assuming that you do nothing at all. This can be fight specific, as you've suggested earlier. Functionally, this is similar to what we have at the moment, except that you can't just use your invuln early in the fight and let the recast start ticking again. You have to build up to it first.

However, you also have ways of building personal LB gauge, that can (and should) be role specific. In the case of tanks, let's say that every time that you use a single target defensive cooldown to mitigate damage, you build gauge based on how much you mitigate. Raw Intuition yourself, gain a bit of personal LB gauge. Use intervention an ally when they're taking damage, gain a bit of personal LB gauge. Naturally, if you use these abilities and don't mitigate anything, you don't gain any benefit. Similar to team LB generation, you can create a list of player-driven conditions that are rewarded by generating gauge.

Now when you max your gauge, like the LB button, you can use the ability at any time you feel like it to give yourself invuln status (either your HP cannot go below 1, or you cannot take damage) coupled with an offensive boost/other benefits for let's say 10 seconds. These can be thematically appropriate to the job. Your gauge then resets to zero and starts building again.

I think that this is a reasonable alternative to nuking invulns from orbit, which I have previously been partial to.