I suggest a new trait, Adrenaline Rush:
If your opponent has initiative, this creature gains the fast trait. If you have initiative this creature gains the slow trait.
You can think of an enchantment that gives charge+1 and adrenaline rush trait or a creature that inherently has it, like Flesh Golem.
Alternatively you can make the fast/slow depend on the round the creature/enchantment is cast. To keep track you could use two different tokens (one if he is cast while you have ini, another one if he is cast while your opponent has ini).
The cool aspect of this trait is that it increases tactical flexibility, the importance of positioning and playing around initiative.
Burning Wings:
Equipment slot: Helmet
The mage gains the flying trait. During each upkeep phase put a load token on Burning Wings. If there are 2 load tokens, destroy Burning Wings.
This would be a cool thematic equipment. Flying on mage is powerful, but since it lasts only 2 rounds and is no enchantment which can be used to surprise, it might not be too powerful. I guess with appropriate mana costs it will be balanced.
Alternatively you could think of a new trait for equipments or enchantments that are inherently very strong:
Corroding X: During each upkeep phase put a load token on this equipment/enchantment. If there are X load tokens, destroy this equipment/enchantment. It could be possible to give the player the choice to pay more mana to increase X.
