So. Update. Managed to score a locked Titan 226. Allowing me to run Titan brakes at all 4 corners and no spacers. There are of course other considerations for the braking system, but I've done research all morning and it seems pretty straightforward.
Titan brake booster and master cylinder, plug the forward pressure sensor tap on the Titan MC because the X only has one, external reservoir for the clutch, and then have the dealership power bleed everything.
From my reading the ABS pump should be fine and all of the sensors for the Titan are compatible with the X computer.
So, full Titan width front and rear, OE Titan wheels, no spacers, everything works. Right?