FUCK Penance. Got his ass. Final game time - 140:35:49.
I crafted THREE sets of end-game armor.
Defense +20%
Auto-Haste
Auto-Protect
Auto-Potion
That failed miserably, and took forever waiting for potions to go off. Also requires a minimum of four uses of Rikku's Overdrive to Mix Hyper Mighty G, Ultra Null-All, Trio of 9999 and Eccentrick.
Break HP Limit
Ribbon
Auto-Haste
Auto-Regen
This was my Dark Aeon/Creation armor. I didn't expect it to work well against Penance, and it did not.
Break HP Limit
Auto-Haste
Auto-Protect
Auto-Regen
This one worked. I was getting too impatient, and had gotten too used to relying on Attack Reels. Quick Hit is really all you need, here, and Eccentrick and Trio of 9999 are useless, massively speeding up the process of trying to get Rikku into Overdrive, or wasting a turn using Entrust.
I achieved my goal of a sub-150-hour 100% completion run.
Mostly. Still have to trek Kimahri, Lulu, Yuna and Auron around their Sphere Grids to max them out, but that won't take more than maybe an hour per character.
I have fully and truly stomped this game into the ground, and I am satisfied.