In the new F@F Severlin acknowledged the deficiency in the Archimage Tree. It takes a lot of work to build an Enhancement tree. Even the fantasy ones that I do. I research a lot and ten try to marry my knowledge of 3.5 and DDO to come up with someone can read and discuss.
It's much less effort to just find the founding principles of a tree than to build a whole tree.
Archimage. Your studies have taken you across the Planes. Across the multiverse. You had tea with Mordenkainen, drank the tears of sorrow and isolation that such commitment requires, You have seen realities Elminster himself has not heard of. Mystra guides you. But you are in control. Willpower incarnate.
No matter the personal cost. You cannot be bested.
You acquire CounterSpell Stance. This stance is a Big Daddy stance like the One SSG introduced that limits the use of other stances.
This stance is affected by all Metamagic feats. While active it steadily drains your mana. When you are targeted with a damaging spell you automatically cast the spell at its attacker. Each returned spell costs an additional 4 sp. New animations for CounterSpell.
While in this stance you cannot be damaged or controlled by mortal spellcasters.
You have seen the deep magic that comes from nothing. While you cannot describe the infinity you saw, your grasp of your own reality is flawed only by the shackles of time and it's perpetual march forward.
You gain the feat Mystery of Mana this feat acts like Wholeness of Body only it restores an amount of Mana based on your core enhancements taken in Archmage. Limited by charges as well.
You gain the SLA Lash. You can drive enemies back with a Lash Made of Magic. Whip attack that pushes enemies back and slows them. Additional upgrades add trip. Cooldown dependant. 10 sp.