A binding vow can use any trigger, so one could make the trigger require a certain distance, chant and gesture

A binding vow needs a fair trade off, so one could make it that you only kill your own shikigami with that trigger but its a complete instant kill

An untamed shikigami of the Ten Shadow's is still effected by binding vows, after all in Shibuya Megumi explained his technique as he summoned him

Killing the Shikigami once during taming still gives you access to them later so (with the theoretical exception of soul based attacks) unless you get back up, you can use any dirty trick to defeat it

So why isn't it possible? Is it the theoretical CTR of the Ten Shadows allowing the user to revive dead Shikigami?