Your ability to augment your weapons with magical energy has reached an intuitive level.
Prerequisites: Arcane Strike, caster level 9th.
Benefit: You may use Arcane Strike as a free action.
Normal: Using Arcane Strike is a swift action.
Were activating Arcane Strike a free action it wouldn't interfere with an EK's ability to use Spell Critical, or any other arcane spellcaster's ability to cast quickened spells.
What do all y'all think?
I don't think it's game-breaking to let the feat be a free action in the first place, but that's just me.
Our home-brew feat
Improved Arcane Strike
You can sacrifice your arcane power to enhance your weapons with magical energy.
Prerequisites: Arcane strike, base attack bonus +9.
Benefits: As a swift action, you can sacrifice an arcane spell to receive a bonus to damage equal to your primary spellcasting ability modifier for a number of rounds equal to the level of the spell sacrificed. Furthermore, you can use arcane strike as a free action.
Normal: Using arcane strike is a swift action.
In a setting where said bonus is around +5 buffed at lv1, +12 at lv20.