Hrmn... you know...

What if, 'Overhealing,' was a mechanic? So say your Warrior has 50,000 HP. They're at 50,000, you slap down a Lustrate/Tetra/Whatever, and instead of the HP staying 50,000, it instead goes up to 65,000? It could make for an interesting mechanic in Boss Fights, beefing up the tank's health so they can take crazy damage. Or beefing up the party's health to take a big damage move. As for visually referencing it, the Green HP bar gets a pink/purple one over it. Double health? A Blue one.