I have a crazy idea. First, add extra sources of fate points (like odd epic levels, or maxing out an entire ED sphere), then add one (or more) extra Twist of Fate slot. This slot, however, is a bit different than the others. First of all, you can't put any passive ability in it. Secondly, it's cheaper to upgrade it. This is called an Epic Spell Slot. That is, however, only half of it.
All available twists that can be put into your E.S.S. will appear in your Epic Spell Book (probably something you'll have to pay for). Other Epic spells can be added to the list, but you'll have to find them, first. Some will appear in quest chain end rewards, while others will be raid loot. Due to the difficulty in finding them, the epic spells will have to be epic. CitW might drop a Mass Web spell, or a Summon Epic Draegoloth spell, for instance. The Fall of Truth raid night drop a wide-area Epic Chain Lightning spell. There are many possibilities.
Epic spells don't have to be just mana abilities, however. There is no reason for there not to be epic monk abilities, like AoE finishing moves.
What do you all think?