Most player-created potions grant a finite amount of resource restoration. At higher levels, is there some way to create a "Potion of Ultimate x", such as those that can occasionally be found in the wild or bought, which will restore the user's resource completely?
No. You cannot craft potions that will, for example, fill your health bar completely, no matter your HP deficit. However, you can create potions of sufficient potency that they will be functionally identical if you grab the right key perks and abuse enchanting while you're at it.