I realize this thread is a bit old, but just had to say that DAMN I soooooooooooo loved the original Warhammer IIC !!! It's replacement just looks sad and ridiculous to me.
Also - I just got my hands on the Spartan/Phalanx set and the Tomahawk/Defender set, and have mixed thoughts on them.
At first glance the Tomahawk is a terrific substitute for the old unseen Warhammer and the Phalanx is also a great substitute for the old unseen Longbow. The Spartan is just a bit smallish, but a very usable replacement for the old unseen Archer and is almost exactly the same size as the older unseen mini with it's arms down by it's sides. The Defender has the same body size as the unseen Rifleman, but it's arms are terrible and way to narrow/skinny.
For use with Battletech, the Tomahawk/Warhammer and the Phalanx/Longbow are both perfect. Mounted on a IWM hex base the Spartan/Archer works very well too, though it's upper arms are just a bit thin. To utilize the Defender/Rifleman you'd probably have to find a way to widen the arms and the width between the barrels, as well as probably replace the barrels.
Should be getting my hands on the Valkyries pretty soon, and have some high hopes for them.