Something 4e missed from Tome of Battle Book of 9 Swords

The book of 9 Swords has some slick elements many were brought in to 4e but not all.

An element that was missing was the use of cross class maneuver lists. These lists were like schools of magic... but also like flavors of martial arts. In effect a Class defined several of the lists you had access to, plus some class features on top of that.

The concept of stances and strikes being the central element of martial moves also matches real world flavor.

The book kind of dripped with flavor in general as well.

I LOVED that book. From what I've read, that book had a lot of the ideas that would eventually shape much of 4E. The concept of limited but auto-renewing resources (daily or encounter powers). Plus it was definitely full of flavor!